Medical Pharmacology: Chapter 31 — Gonadal/Ovarian Pharmacology -- Module 5

Chapter 31 — Gonadal/Ovarian Pharmacology — Module 5 — Androgen Pharmacology

1. Which enzyme is responsible for the conversion of testosterone to estradiol, and what is the approximate contribution of this peripheral conversion to circulating estradiol in men?

A) 5 alpha-reductase (5AR); approximately 80% of male estradiol is produced by 5 alpha-reduction of testosterone in adipose tissue.
B) 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD); approximately 20% of male estradiol is produced by direct testicular secretion.
C) Aromatase (CYP19A1); approximately 80% of circulating estradiol in men is derived from peripheral aromatization of testosterone and androstenedione in adipose tissue, muscle, brain, and other extragonadal sites, with only about 20% secreted directly by the testes.
D) 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD); approximately 50% of male estradiol arises from adrenal conversion of dehydroepiandrosterone.
E) CYP17A1 (17-hydroxylase/17,20-lyase); essentially all male estradiol is produced directly within Leydig cells without a peripheral contribution.

ANSWER: C

Rationale:

Option C is correct. Aromatase, encoded by the CYP19A1 gene, catalyzes the conversion of testosterone to estradiol (and androstenedione to estrone) through aromatization of the steroid A-ring. In men, approximately 80% of circulating estradiol is derived from peripheral aromatization of androgens in extragonadal tissues — principally adipose tissue, but also skeletal muscle, brain, and bone — while only about 20% is secreted directly by the testes. This peripheral estradiol production is physiologically essential in men: estradiol maintains bone mineral density, mediates epiphyseal growth plate closure, contributes to gonadotropin negative feedback, and supports libido. The clinical relevance for androgen pharmacology is that supraphysiological testosterone (from high-dose TRT or anabolic-androgenic steroid use) increases substrate for aromatization proportionally, raising estradiol and producing gynecomastia and fluid retention.

Option A: Option A is incorrect; 5 alpha-reductase converts testosterone to dihydrotestosterone (DHT), not to estradiol. 5AR produces a more potent androgen, not an estrogen.
Option B: Option B is incorrect; 17 beta-HSD catalyzes interconversion of androstenedione and testosterone (and of estrone and estradiol), not the aromatization of testosterone to estradiol, and the figure misassigns the peripheral/testicular split.
Option D: Option D is incorrect; 3 beta-HSD catalyzes conversion of delta-5 steroids (pregnenolone, 17-hydroxypregnenolone, DHEA) to delta-4 steroids in the steroidogenic pathway, not aromatization to estradiol.
Option E: Option E is incorrect; CYP17A1 is the 17-hydroxylase/17,20-lyase enzyme required for androgen precursor synthesis, not aromatization, and the claim that all male estradiol is testicular in origin is contradicted by the predominant peripheral contribution.

2. In the testicular steroidogenic pathway, which enzyme catalyzes the final step producing testosterone, and what reaction does it perform?

A) 17 beta-hydroxysteroid dehydrogenase type 3 (encoded by HSD17B3), which reduces androstenedione to testosterone in the Leydig cells as the final step of testicular androgen biosynthesis.
B) Aromatase (CYP19A1), which reduces androstenedione directly to testosterone within the seminiferous tubules.
C) 5 alpha-reductase type 2 (encoded by SRD5A2), which converts androstenedione to testosterone in peripheral target tissues.
D) 3 beta-hydroxysteroid dehydrogenase, which oxidizes dehydroepiandrosterone directly to testosterone in a single enzymatic step.
E) CYP11A1 (cholesterol side-chain cleavage enzyme), which converts androstenedione to testosterone as the rate-limiting final reaction of steroidogenesis.

ANSWER: A

Rationale:

Option A is correct. Testosterone biosynthesis proceeds from cholesterol through the steroidogenic pathway: cholesterol to pregnenolone (by CYP11A1, the cholesterol side-chain cleavage enzyme and rate-limiting step), then through progesterone or the delta-5 pathway to 17-hydroxylated intermediates (via CYP17A1), to androstenedione, and finally to testosterone. The terminal reaction — reduction of the 17-keto group of androstenedione to the 17 beta-hydroxyl of testosterone — is catalyzed by 17 beta-hydroxysteroid dehydrogenase type 3, encoded by the HSD17B3 gene, which is expressed predominantly in the Leydig cells of the testis. Loss-of-function mutations in HSD17B3 produce a form of 46,XY disorder of sex development due to impaired testosterone synthesis.

Option B: Option B is incorrect; aromatase (CYP19A1) converts androgens to estrogens (testosterone to estradiol, androstenedione to estrone) and does not produce testosterone.
Option C: Option C is incorrect; 5 alpha-reductase type 2 converts testosterone to dihydrotestosterone in target tissues — it acts downstream of testosterone, not on androstenedione, and does not synthesize testosterone.
Option D: Option D is incorrect; 3 beta-hydroxysteroid dehydrogenase converts delta-5 steroids to delta-4 steroids (e.g., DHEA to androstenedione) but does not catalyze the single-step conversion of DHEA to testosterone.
Option E: Option E is incorrect; CYP11A1 catalyzes the first and rate-limiting step of steroidogenesis (cholesterol to pregnenolone), not the final conversion of androstenedione to testosterone.

3. During normal male fetal development, which statement correctly distinguishes the androgen responsible for internal male duct development from the androgen responsible for external genital virilization?

A) Both internal Wolffian duct development and external genital virilization require dihydrotestosterone (DHT); testosterone has no independent role in fetal sexual differentiation.
B) Both internal Wolffian duct development and external genital virilization require testosterone; DHT plays no role until puberty.
C) Estradiol drives internal Wolffian duct development, while testosterone drives external genital virilization.
D) Testosterone drives external genital virilization, while DHT drives internal Wolffian duct development into the epididymis, vas deferens, and seminal vesicles.
E) Testosterone drives differentiation of the Wolffian ducts into the epididymis, vas deferens, and seminal vesicles (internal structures), while dihydrotestosterone (DHT) — produced locally by type 2 5 alpha-reductase — is required for virilization of the external genitalia (penis, scrotum, prostate).

ANSWER: E

Rationale:

Option E is correct. Male fetal sexual differentiation depends on a tissue-selective division of labor between testosterone and dihydrotestosterone (DHT). Testosterone, secreted by the fetal Leydig cells, acts directly on the androgen receptor in the Wolffian (mesonephric) ducts to drive their differentiation into the epididymis, vas deferens, and seminal vesicles — the internal male reproductive structures. DHT, produced locally from testosterone by type 2 5 alpha-reductase in the tissues of the urogenital sinus and genital tubercle, is required for virilization of the external genitalia (formation of the penis and scrotum) and for prostate development. This is why congenital type 2 5 alpha-reductase (SRD5A2) deficiency produces a 46,XY individual with normal internal male structures (testosterone-dependent) but ambiguous or female-appearing external genitalia at birth (DHT-dependent), with virilization occurring at puberty when the testosterone surge partially compensates.

Option A: Option A is incorrect; internal Wolffian duct development requires testosterone, not DHT. Assigning both processes to DHT contradicts the SRD5A2 deficiency phenotype, in which internal structures form normally despite absent DHT.
Option B: Option B is incorrect; external genital virilization specifically requires DHT, not testosterone alone, as demonstrated by the failure of external virilization in SRD5A2 deficiency despite intact testosterone.
Option C: Option C is incorrect; estradiol does not drive Wolffian duct development. Wolffian differentiation is a testosterone-dependent, androgen receptor-mediated process.
Option D: Option D is incorrect; it inverts the correct assignments — testosterone drives the internal structures and DHT drives the external genitalia, the opposite of what this option states.

4. Which of the following correctly groups conditions by their effect on sex hormone-binding globulin (SHBG) concentration?

A) Aging, obesity, and hyperthyroidism all increase SHBG; insulin resistance and estrogen administration all decrease SHBG.
B) Aging, estrogen administration, hyperthyroidism, and hepatic cirrhosis increase SHBG, whereas obesity, insulin resistance, hypothyroidism, and exogenous androgens decrease SHBG.
C) Obesity, insulin resistance, and exogenous androgens increase SHBG; aging and estrogen administration decrease SHBG.
D) All listed conditions — aging, obesity, hyperthyroidism, hypothyroidism, and estrogen use — increase SHBG to a similar degree, so SHBG measurement adds no interpretive value.
E) Estrogen administration and exogenous androgens both increase SHBG, while hyperthyroidism and hypothyroidism both decrease it.

ANSWER: B

Rationale:

Option B is correct. SHBG concentration is dynamically regulated, and recognizing the direction of change is essential for interpreting total testosterone values, since SHBG-bound testosterone is not bioavailable. Conditions that increase SHBG include aging, estrogen administration (oral estrogen raises hepatic SHBG synthesis), hyperthyroidism, and hepatic disease/cirrhosis. Conditions that decrease SHBG include obesity, insulin resistance and type 2 diabetes, hypothyroidism, and exogenous androgen administration. When SHBG is high, total testosterone may appear falsely reassuring while bioavailable testosterone is reduced; when SHBG is low, total testosterone may appear low while bioavailable testosterone remains relatively preserved. This is why calculated free testosterone or a direct free testosterone assay is needed when an SHBG disturbance is suspected.

Option A: Option A is incorrect; it misassigns obesity as SHBG-increasing (obesity lowers SHBG) and estrogen as SHBG-decreasing (estrogen raises SHBG). Hyperthyroidism does raise SHBG, but the other assignments are wrong.
Option C: Option C is incorrect; it inverts the obesity, insulin resistance, exogenous androgen group (these decrease SHBG, not increase it) and the aging/estrogen group (these increase SHBG, not decrease it).
Option D: Option D is incorrect; the listed conditions do not all move SHBG in the same direction, and SHBG measurement is in fact interpretively valuable precisely because conditions move it in opposite directions.
Option E: Option E is incorrect; exogenous androgens decrease SHBG (not increase it), and hyperthyroidism increases SHBG while hypothyroidism decreases it — the two thyroid states move SHBG in opposite directions, not the same direction.

5. Which of the following correctly ranks three injectable testosterone ester formulations by their approximate elimination half-life and corresponding dosing interval?

A) Testosterone undecanoate has the shortest half-life (about 4 days) and requires weekly injection, while testosterone enanthate has the longest half-life (about 21 days) and is dosed every 10 to 14 weeks.
B) All three esters — enanthate, cypionate, and undecanoate — share an identical half-life of approximately 8 days and are dosed every 2 weeks; the ester chain length does not affect pharmacokinetics.
C) Testosterone cypionate has a markedly longer half-life (about 21 days) than testosterone undecanoate (about 8 days), so cypionate is the agent dosed every 10 to 14 weeks.
D) Testosterone enanthate has a half-life of approximately 7 to 8 days and testosterone cypionate approximately 8 to 10 days, both dosed every 1 to 2 weeks; testosterone undecanoate has a much longer half-life of approximately 21 days and is dosed every 10 to 14 weeks after a loading regimen.
E) Testosterone enanthate and cypionate both have half-lives of approximately 21 days and are dosed every 10 to 14 weeks, while testosterone undecanoate has a half-life of approximately 7 days requiring weekly injection.

ANSWER: D

Rationale:

Option D is correct. The injectable testosterone esters differ in elimination half-life as a function of their ester side-chain, which governs the rate of release from the intramuscular oil depot. Testosterone enanthate has a half-life of approximately 7 to 8 days and testosterone cypionate approximately 8 to 10 days; both are administered every 1 to 2 weeks (or weekly to reduce peak-to-trough fluctuation). Testosterone undecanoate, with its longer undecanoate ester chain in a castor oil vehicle, has a substantially longer half-life of approximately 21 days and is administered every 10 to 14 weeks following a loading injection given 6 weeks after the first dose, producing more stable serum levels but requiring the 30-minute post-injection observation for pulmonary oil microembolism risk.

Option A: Option A is incorrect; it inverts the half-lives — undecanoate is the long-acting agent (about 21 days), not enanthate, and enanthate is not dosed every 10 to 14 weeks.
Option B: Option B is incorrect; the three esters do not share an identical half-life. Ester chain length directly determines the depot release rate and therefore the half-life and dosing interval.
Option C: Option C is incorrect; cypionate does not have a 21-day half-life. Undecanoate is the long-acting ester dosed every 10 to 14 weeks; cypionate is dosed every 1 to 2 weeks.
Option E: Option E is incorrect; enanthate and cypionate do not have 21-day half-lives, and undecanoate is not a weekly short-acting agent — this inverts the actual pharmacokinetics.

6. Which of the following correctly distinguishes transdermal testosterone gels from transdermal testosterone patches with respect to their characteristic adverse effects?

A) Testosterone gels carry a notable risk of accidental transfer of drug to female partners or children through skin contact, whereas testosterone patches (Androderm) are characterized by a high rate of local skin reactions at the application site, occurring in approximately 35% to 50% of users.
B) Testosterone gels frequently cause application-site skin necrosis, whereas testosterone patches carry essentially no risk of skin reaction and no risk of secondary transfer.
C) Both gels and patches carry an identical and equal risk of secondary transfer to household contacts, and neither produces application-site skin reactions.
D) Testosterone patches carry the primary risk of secondary transfer to partners and children, whereas gels are notable chiefly for application-site skin reactions in the majority of users.
E) Neither gels nor patches produce any meaningful local skin reaction or transfer risk; both are pharmacokinetically and dermatologically equivalent to intramuscular injection.

ANSWER: A

Rationale:

Option A is correct. Although both are transdermal delivery systems, gels and patches have distinct characteristic adverse effects. Testosterone gels (AndroGel, Testim, Fortesta) carry a well-documented risk of secondary exposure: drug can transfer from the application site to female partners or children through direct skin contact or contact with contaminated surfaces, producing virilization or pseudoprecocious puberty. This risk drives the counseling requirements to wash hands, cover the site, and avoid skin-to-skin contact. Testosterone patches (Androderm), by contrast, are an occlusive system whose most characteristic adverse effect is local skin reaction (erythema, pruritus, irritation, occasionally blistering) at the application site, occurring in approximately 35% to 50% of users — a frequency that limits patch tolerability. The secondary-transfer risk is much lower with patches because the drug is contained within the adhesive system rather than applied as an open film.

Option B: Option B is incorrect; gels do not characteristically cause skin necrosis, and patches do produce frequent application-site skin reactions.
Option C: Option C is incorrect; the two systems do not carry identical transfer risk, and patches do produce frequent local skin reactions.
Option D: Option D is incorrect; it inverts the two characteristic effects — secondary transfer is the gel-associated risk, and frequent application-site skin reaction is the patch-associated effect.
Option E: Option E is incorrect; both transdermal systems have meaningful dermatologic considerations (transfer for gels, local reaction for patches), and transdermal delivery is pharmacokinetically distinct from intramuscular injection, producing more stable levels without the injectable peak-to-trough pattern.

7. Which of the following correctly distinguishes finasteride from dutasteride with respect to 5 alpha-reductase isoform selectivity and the degree of serum dihydrotestosterone (DHT) suppression each achieves?

A) Finasteride is a dual type 1 and type 2 inhibitor achieving about 90% serum DHT suppression; dutasteride is type 2-selective achieving about 70%.
B) Both finasteride and dutasteride are type 2-selective inhibitors achieving identical serum DHT suppression of approximately 70%, differing only in half-life.
C) Finasteride is approximately 100-fold selective for the type 2 isoform and reduces serum DHT by approximately 70%; dutasteride is a non-selective dual inhibitor of both type 1 and type 2 isoforms and reduces serum DHT by approximately 90% to 95%.
D) Finasteride is type 1-selective and dutasteride is type 2-selective; both achieve about 50% serum DHT suppression, which is the class ceiling.
E) Dutasteride is type 2-selective achieving 70% suppression, while finasteride inhibits neither isoform directly but instead blocks the androgen receptor, producing about 95% functional DHT blockade.

ANSWER: C

Rationale:

Option C is correct. Finasteride is approximately 100-fold selective for type 2 5 alpha-reductase (the predominant prostatic and scalp isoform encoded by SRD5A2) and reduces serum DHT by approximately 70% while reducing intraprostatic DHT by over 90%. Dutasteride is a non-selective dual inhibitor of both type 1 (SRD5A1, predominantly hepatic/peripheral) and type 2 isoforms, and achieves greater systemic DHT suppression of approximately 90% to 95%. Despite dutasteride's greater serum DHT suppression, head-to-head trials have not shown meaningfully superior BPH outcomes, because both agents suppress intraprostatic DHT comparably.

Option A: Option A is incorrect; it inverts the two agents — finasteride is the type 2-selective agent (about 70% serum DHT reduction), and dutasteride is the dual inhibitor (about 90–95%).
Option B: Option B is incorrect; the two agents are not both type 2-selective with identical suppression — dutasteride is a dual inhibitor with greater serum DHT suppression than finasteride.
Option D: Option D is incorrect; finasteride is type 2-selective, not type 1-selective, and the suppression figures (about 70% for finasteride, 90–95% for dutasteride) exceed a 50% class ceiling.
Option E: Option E is incorrect; finasteride is a 5 alpha-reductase inhibitor, not an androgen receptor blocker. It acts enzymatically to reduce DHT production, not by competitive AR antagonism.

8. Human chorionic gonadotropin (hCG) and clomiphene citrate are both used to stimulate endogenous testosterone production while preserving fertility. Which of the following correctly distinguishes their mechanisms of action?

A) Both hCG and clomiphene act directly as luteinizing hormone (LH) receptor agonists on Leydig cells; they differ only in route of administration.
B) hCG blocks hypothalamic estrogen receptors to raise LH and FSH, while clomiphene directly stimulates Leydig cell LH receptors.
C) Both hCG and clomiphene act by blocking aromatase, thereby reducing estradiol negative feedback and raising gonadotropin secretion.
D) hCG is a selective estrogen receptor modulator that raises gonadotropins centrally, while clomiphene is an LH analog that acts peripherally on the testis.
E) hCG acts as a luteinizing hormone (LH) receptor agonist directly on testicular Leydig cells, maintaining intratesticular testosterone without engaging the hypothalamic-pituitary axis, whereas clomiphene citrate is a selective estrogen receptor modulator (SERM) that blocks estrogen receptor-mediated negative feedback at the hypothalamus, raising endogenous LH and FSH secretion.

ANSWER: E

Rationale:

Option E is correct. Although hCG and clomiphene are both used to stimulate endogenous testosterone while preserving spermatogenesis, they act at different levels of the hypothalamic-pituitary-gonadal axis. Human chorionic gonadotropin (hCG) structurally and functionally mimics LH and acts as a direct agonist at the LH receptor on testicular Leydig cells, driving intratesticular testosterone production directly without requiring an intact hypothalamic-pituitary axis. Clomiphene citrate is a selective estrogen receptor modulator (SERM) that antagonizes estrogen receptors at the hypothalamus, interrupting the estrogen-mediated negative feedback that normally restrains GnRH pulsatility; this raises endogenous LH and FSH secretion, which in turn stimulates both testosterone production and spermatogenesis through the patient's own pituitary-gonadal axis. The key discrimination is the level of action: hCG works at the testis (downstream), clomiphene works at the hypothalamus (upstream).

Option A: Option A is incorrect; clomiphene is not an LH receptor agonist. Only hCG acts directly at the LH receptor; clomiphene acts centrally as a SERM.
Option B: Option B is incorrect; it inverts the two mechanisms — hCG is the direct Leydig cell LH-receptor agonist, and clomiphene is the central estrogen receptor blocker.
Option C: Option C is incorrect; neither hCG nor clomiphene acts primarily as an aromatase inhibitor. Aromatase inhibition (e.g., anastrozole) is a separate pharmacological strategy.
Option D: Option D is incorrect; it inverts the two mechanisms — clomiphene is the SERM acting centrally, and hCG is the LH-mimetic acting on the testis.

9. Among the anti-androgens, which agent does NOT suppress gonadotropin secretion, and what is the pharmacological reason for this distinction?

A) Cyproterone acetate does not suppress gonadotropin secretion because it lacks progestogenic activity; spironolactone and bicalutamide both strongly suppress LH and FSH.
B) Bicalutamide does not suppress gonadotropin secretion because it is a pure non-steroidal androgen receptor antagonist lacking progestogenic activity; by blocking the androgen receptor at the hypothalamus and pituitary it removes testosterone negative feedback, causing LH to rise. By contrast, cyproterone acetate (a steroidal progestin) strongly suppresses gonadotropins through progesterone receptor-mediated feedback.
C) Spironolactone does not suppress gonadotropin secretion because it is a pure androgen receptor agonist; bicalutamide and cyproterone both suppress LH through progestogenic activity.
D) All three agents — spironolactone, cyproterone acetate, and bicalutamide — equally and strongly suppress gonadotropin secretion through identical progesterone receptor-mediated mechanisms.
E) Enzalutamide is the only anti-androgen that does not suppress gonadotropins; bicalutamide, cyproterone, and spironolactone all act as potent gonadotropin suppressants through GABA-A receptor modulation.

ANSWER: B

Rationale:

Option B is correct. The discrimination among anti-androgens by their effect on gonadotropin secretion rests on whether the agent has progestogenic (anti-gonadotropic) activity. Bicalutamide is a pure non-steroidal androgen receptor (AR) antagonist with no progestogenic activity; it does not suppress gonadotropin secretion. By blocking the AR at the hypothalamus and pituitary, it actually removes testosterone's negative feedback, so LH rises and circulating testosterone increases approximately 1.5-fold during monotherapy. In contrast, cyproterone acetate is a steroidal compound with potent progestogenic activity that suppresses LH and FSH through progesterone receptor-mediated negative feedback, reducing testicular testosterone production in addition to its AR blockade. Spironolactone, a steroidal MR antagonist with AR-blocking activity, has weaker effects on the gonadotropin axis than cyproterone but does produce some HPG perturbation, particularly menstrual irregularity in women; it is not the cleanest example of "no gonadotropin suppression," whereas bicalutamide is the canonical non-suppressing anti-androgen.

Option A: Option A is incorrect; it misassigns the non-suppressing agent. Cyproterone acetate strongly suppresses gonadotropins through its progestogenic activity — it is the opposite of a non-suppressor.
Option C: Option C is incorrect; spironolactone is an AR antagonist, not an AR agonist, and bicalutamide does not have progestogenic activity.
Option D: Option D is incorrect; the three agents do not equally suppress gonadotropins through identical mechanisms — bicalutamide does not suppress them at all, and only cyproterone has potent progesterone receptor-mediated suppression.
Option E: Option E is incorrect; bicalutamide, not enzalutamide, is the example here, and the anti-androgens do not suppress gonadotropins through GABA-A modulation (GABA-A modulation is enzalutamide's seizure-related CNS mechanism, unrelated to gonadotropin feedback).

10. Which of the following correctly classifies bicalutamide and cyproterone acetate by steroidal versus non-steroidal structure and identifies a serious adverse effect characteristic of each?

A) Both bicalutamide and cyproterone acetate are non-steroidal androgen receptor antagonists; both share an identical adverse effect profile dominated by meningioma risk.
B) Bicalutamide is a steroidal progestin whose characteristic serious risk is venous thromboembolism; cyproterone acetate is non-steroidal and its characteristic risk is hepatotoxicity.
C) Both agents are steroidal compounds; bicalutamide's characteristic risk is meningioma and cyproterone's is gynecomastia, reflecting their shared progestogenic activity.
D) Bicalutamide is a non-steroidal androgen receptor antagonist whose characteristic serious adverse effect is hepatotoxicity (occurring in approximately 1% to 3% of patients), while cyproterone acetate is a steroidal anti-androgen and progestin whose characteristic serious risks include dose- and duration-dependent meningioma and venous thromboembolism.
E) Bicalutamide is non-steroidal and entirely free of serious adverse effects; cyproterone acetate is steroidal and its only notable effect is mild gynecomastia.

ANSWER: D

Rationale:

Option D is correct. Bicalutamide and cyproterone acetate differ in both chemical structure and characteristic toxicity. Bicalutamide is a non-steroidal androgen receptor antagonist; its most serious characteristic adverse effect is hepatotoxicity, which occurs in approximately 1% to 3% of patients and warrants baseline and periodic liver function monitoring. Gynecomastia and breast tenderness are also common with bicalutamide monotherapy due to elevated testosterone aromatizing to estradiol. Cyproterone acetate is a steroidal anti-androgen with potent progestogenic activity; its characteristic serious risks include a dose- and duration-dependent increase in meningioma incidence (demonstrated in French pharmacovigilance data and leading to regulatory restrictions) and venous thromboembolism (attributed to its progestogenic activity), in addition to hepatotoxicity that is generally more serious than that of bicalutamide.

Option A: Option A is incorrect; cyproterone acetate is a steroidal compound, not non-steroidal, and the two agents do not share an identical meningioma-dominated profile — meningioma is a cyproterone-specific concern.
Option B: Option B is incorrect; it inverts the structural classifications — bicalutamide is non-steroidal and cyproterone is steroidal — and misassigns the characteristic risks.
Option C: Option C is incorrect; bicalutamide is non-steroidal (not steroidal) and lacks progestogenic activity, and meningioma is a cyproterone-associated risk, not a bicalutamide-associated one.
Option E: Option E is incorrect; bicalutamide is not free of serious adverse effects (hepatotoxicity is a recognized risk), and cyproterone's risks extend well beyond mild gynecomastia to include meningioma and thromboembolism.

11. Which of the following correctly distinguishes enzalutamide from bicalutamide in terms of receptor pharmacology and central nervous system (CNS) effects?

A) Enzalutamide binds the androgen receptor with approximately 5 to 8 times greater affinity than bicalutamide, additionally inhibits nuclear translocation of the AR-ligand complex and AR binding to DNA, and carries a distinctive CNS profile including fatigue, cognitive impairment, and a seizure risk attributable to negative allosteric modulation of GABA-A receptors — effects not seen with bicalutamide.
B) Bicalutamide binds the androgen receptor with greater affinity than enzalutamide and is the agent associated with seizure risk through GABA-A modulation, whereas enzalutamide has no CNS effects.
C) Enzalutamide and bicalutamide bind the androgen receptor with identical affinity and have identical CNS profiles; the only difference between them is oral bioavailability.
D) Enzalutamide acts by suppressing gonadotropin secretion while bicalutamide acts by blocking the androgen receptor; neither agent has any CNS effect.
E) Enzalutamide is a steroidal anti-androgen that lowers the seizure threshold by enhancing GABA-A receptor activity, whereas bicalutamide is non-steroidal and raises the seizure threshold.

ANSWER: A

Rationale:

Option A is correct. Enzalutamide is a second-generation non-steroidal androgen receptor (AR) antagonist developed to overcome resistance to first-generation agents such as bicalutamide. It binds the AR with approximately 5 to 8 times greater affinity than bicalutamide, and beyond simple competitive binding it also inhibits nuclear translocation of the AR-ligand complex and impairs AR binding to DNA and coactivator recruitment, producing more complete AR pathway blockade. Enzalutamide additionally has a distinctive CNS adverse effect profile — fatigue, cognitive impairment, and a seizure risk of approximately 0.5% per year — attributable to its activity as a negative allosteric modulator of GABA-A receptors, which lowers the seizure threshold. These CNS effects are not characteristic of bicalutamide, which does not cross into this pharmacology.

Option B: Option B is incorrect; it inverts the affinity relationship (enzalutamide has higher affinity) and misassigns the seizure risk to bicalutamide.
Option C: Option C is incorrect; the two agents do not bind with identical affinity or have identical CNS profiles — these are precisely the discriminating features.
Option D: Option D is incorrect; enzalutamide does not act by suppressing gonadotropins; it is an AR antagonist like bicalutamide, and enzalutamide does have CNS effects.
Option E: Option E is incorrect; enzalutamide is non-steroidal (not steroidal), and it lowers the seizure threshold by acting as a negative (not positive) allosteric modulator of GABA-A receptors — enhancing GABA-A activity would raise, not lower, the seizure threshold.

12. Which of the following correctly defines the AR-V7 androgen receptor splice variant and explains why it confers resistance to competitive androgen receptor (AR) antagonists?

A) AR-V7 is a point mutation in the AR ligand-binding domain that converts antagonists into agonists, so AR antagonists paradoxically activate it.
B) AR-V7 is a gene amplification that increases the number of full-length AR copies, overwhelming the available antagonist; it retains the ligand-binding domain and responds to higher antagonist doses.
C) AR-V7 is a constitutively active, truncated AR splice variant that lacks the C-terminal ligand-binding domain (LBD) entirely; because all competitive AR antagonists bind to the LBD, a receptor lacking the LBD cannot be blocked by any ligand-competitive antagonist, and AR-V7 activates target genes without requiring androgen.
D) AR-V7 is an extracellular soluble fragment of the AR that sequesters circulating testosterone, lowering androgen availability and thereby mimicking castration; it does not affect antagonist binding.
E) AR-V7 is a variant restricted to the DNA-binding domain that prevents the receptor from entering the nucleus, abolishing all AR signaling and producing androgen independence through loss of function.

ANSWER: C

Rationale:

Option C is correct. AR-V7 (androgen receptor splice variant 7) is a constitutively active, truncated splice variant of the androgen receptor that arises from alternative splicing joining the receptor's N-terminal and DNA-binding domains to a cryptic exon, skipping the exons that encode the C-terminal ligand-binding domain (LBD). Because AR-V7 lacks the LBD entirely, it does not require androgen (testosterone or DHT) to translocate to the nucleus and activate androgen-responsive gene transcription — it is constitutively active. This same structural feature is the basis for its resistance to therapy: all currently approved competitive AR antagonists — bicalutamide, enzalutamide, apalutamide, darolutamide — bind to the LBD to exert their blocking effect. A receptor that lacks the LBD has no binding site for these antagonists and therefore cannot be inhibited by any of them. AR-V7 positivity in circulating tumor cells predicts resistance to AR-pathway-directed therapy and directs treatment toward taxane chemotherapy, which acts independently of AR status.

Option A: Option A is incorrect; AR-V7 is a splice variant lacking the LBD, not a point mutation that converts antagonists to agonists, which is a different and separately described resistance mechanism.
Option B: Option B is incorrect; AR-V7 is not a gene amplification of full-length AR, and it does not retain the LBD — it cannot be overcome by higher antagonist doses precisely because it has no antagonist binding site.
Option D: Option D is incorrect; AR-V7 is not a soluble extracellular fragment that sequesters testosterone; it is an intracellular, constitutively active transcription factor.
Option E: Option E is incorrect; AR-V7 retains the DNA-binding domain and is constitutively active (gain of function in the androgen-independent sense), not a loss-of-function variant that abolishes signaling.

13. Which of the following correctly relates the structural modification of anabolic-androgenic steroids (AAS) to their route of administration and hepatotoxicity?

A) C17-alpha-alkylated AAS are injectable formulations that avoid hepatotoxicity, while 17-beta-esterified AAS are oral agents that cause severe cholestasis.
B) C17-alpha-alkylated AAS (e.g., methyltestosterone, stanozolol, oxandrolone) are orally bioavailable because the 17-alpha-alkyl group blocks first-pass hepatic oxidation, but this same modification impairs hepatic conjugation and excretion and causes hepatotoxicity (cholestasis, peliosis hepatis, hepatocellular tumors); 17-beta-esterified AAS (e.g., nandrolone decanoate) are injectable, undergo normal metabolism after ester cleavage, and do not carry this hepatotoxicity.
C) Both C17-alpha-alkylated and 17-beta-esterified AAS are equally hepatotoxic regardless of route, because all anabolic steroids share the same hepatic metabolic pathway.
D) The 17-beta ester modification confers oral bioavailability and hepatotoxicity, while C17-alpha-alkylation is used only for injectable depot formulations that are hepatically inert.
E) C17-alpha-alkylation makes AAS hepatotoxic by converting them into direct aromatase substrates, generating estrogenic metabolites that injure hepatocytes; injectable esters avoid this by being non-aromatizable.

ANSWER: B

Rationale:

Option B is correct. The structural distinction between oral and injectable AAS determines their hepatotoxicity. C17-alpha-alkylated AAS (methyltestosterone, stanozolol, oxandrolone, oxymetholone) carry a methyl or ethyl group at the 17-alpha carbon that sterically blocks first-pass hepatic oxidation at the adjacent 17-beta hydroxyl, conferring oral bioavailability. However, this same modification impairs the hepatocyte's normal conjugation and biliary excretion of the steroid, producing dose-dependent intrahepatic cholestasis, peliosis hepatis (blood-filled hepatic cysts), and, with prolonged high-dose use, hepatocellular adenoma and carcinoma. Injectable AAS (nandrolone decanoate, boldenone undecylenate, testosterone esters) are esterified at the 17-beta hydroxyl rather than alkylated at 17-alpha; after the ester is cleaved by serum esterases following systemic absorption, the released steroid undergoes normal hepatic metabolism and does not produce the cholestatic or hepatocellular toxicity characteristic of the oral 17-alpha-alkylated agents.

Option A: Option A is incorrect; it inverts the structure-route relationships — C17-alpha-alkylated agents are the oral, hepatotoxic ones, and 17-beta-esterified agents are the injectable, non-hepatotoxic ones.
Option C: Option C is incorrect; oral 17-alpha-alkylated and injectable 17-beta-esterified AAS are not equally hepatotoxic; the structural difference produces a genuine pharmacological difference in hepatic toxicity.
Option D: Option D is incorrect; it reverses the roles — 17-beta-esterification is the injectable, hepatically tolerated route, and 17-alpha-alkylation is the oral, hepatotoxic modification.
Option E: Option E is incorrect; the hepatotoxicity of 17-alpha-alkylated AAS results from impaired conjugation and biliary excretion of the steroid itself, not from conversion into aromatase substrates generating estrogenic hepatotoxins.

14. Which of the following best describes the mechanisms by which testosterone stimulates erythropoiesis, producing the erythrocytosis commonly seen with testosterone replacement therapy?

A) Testosterone stimulates erythropoiesis solely by increasing dietary iron absorption in the duodenum, without any effect on erythropoietin or erythroid progenitor cells.
B) Testosterone suppresses erythropoiesis at low doses and stimulates it only at supraphysiological levels through direct inhibition of renal erythropoietin synthesis.
C) Testosterone increases erythropoiesis exclusively by prolonging the lifespan of circulating mature erythrocytes, with no effect on bone marrow production.
D) Testosterone raises hematocrit only indirectly by causing plasma volume contraction, producing a relative (not absolute) erythrocytosis.
E) Testosterone stimulates erythropoiesis through several converging mechanisms: direct androgen receptor-mediated stimulation of erythroid progenitor cells in the bone marrow, suppression of hepcidin (increasing iron availability for erythropoiesis), and increased erythropoietin production.

ANSWER: E

Rationale:

Option E is correct. Testosterone-induced erythrocytosis — the most common dose-dependent adverse effect of testosterone replacement therapy, occurring in roughly 20% to 40% of men on injectable formulations — results from several converging mechanisms. First, testosterone directly stimulates erythroid progenitor cells in the bone marrow via androgen receptor activation. Second, testosterone suppresses hepcidin, the hepatic peptide that restrains iron availability; lowering hepcidin increases iron delivery to the erythron, supporting hemoglobin synthesis. Third, testosterone increases erythropoietin production (and may reset the erythropoietin-hemoglobin set point), further driving red cell mass. The combined effect raises hematocrit, and a value above 54% is the threshold for intervention (dose reduction, switch to transdermal, or therapeutic phlebotomy) because hyperviscosity increases thrombotic risk.

Option A: Option A is incorrect; iron absorption is only one downstream contributor (via hepcidin suppression), and testosterone also acts directly on progenitors and on erythropoietin — it is not the sole mechanism.
Option B: Option B is incorrect; testosterone stimulates rather than suppresses erythropoiesis, and it increases rather than inhibits erythropoietin production.
Option C: Option C is incorrect; testosterone increases marrow red cell production; it does not act chiefly by prolonging mature erythrocyte lifespan.
Option D: Option D is incorrect; testosterone produces a true (absolute) erythrocytosis through increased red cell mass, not merely a relative rise from plasma volume contraction.

15. A long-term anti-androgen carries a dose- and duration-dependent risk of meningioma that has led to regulatory restrictions in several countries. Which agent is this, and how does this risk discriminate it from other anti-androgens?

A) Finasteride; its meningioma risk arises from chronic dihydrotestosterone suppression in the meninges and distinguishes it from dutasteride, which carries no such risk.
B) Bicalutamide; its meningioma risk derives from elevated testosterone aromatizing to estradiol in the central nervous system and distinguishes it from cyproterone acetate.
C) Spironolactone; its meningioma risk arises from mineralocorticoid receptor blockade in arachnoid tissue and distinguishes it from all other anti-androgens.
D) Cyproterone acetate; its progestogenic activity underlies a well-documented dose- and duration-dependent increase in meningioma incidence (demonstrated in French pharmacovigilance data), a risk not characteristic of the non-steroidal anti-androgens bicalutamide and enzalutamide or of spironolactone and finasteride.
E) Enzalutamide; its meningioma risk is a direct consequence of GABA-A receptor modulation in the meninges and distinguishes it from bicalutamide.

ANSWER: D

Rationale:

Option D is correct. Cyproterone acetate is the anti-androgen associated with a dose- and duration-dependent increase in meningioma incidence. This signal was demonstrated prominently in French pharmacovigilance data showing a clear relationship between cumulative cyproterone exposure (particularly at doses of 25 mg per day or higher over prolonged periods) and meningioma risk, leading to regulatory restrictions and monitoring requirements in several countries. The risk is linked to cyproterone's progestogenic activity, as meningiomas frequently express progesterone receptors. This adverse effect specifically discriminates cyproterone acetate from the other anti-androgens: the non-steroidal AR antagonists bicalutamide and enzalutamide, the MR antagonist spironolactone, and the 5 alpha-reductase inhibitor finasteride do not carry this characteristic meningioma association.

Option A: Option A is incorrect; finasteride is not associated with meningioma; its characteristic concerns are sexual adverse effects and the post-finasteride syndrome debate.
Option B: Option B is incorrect; bicalutamide is not associated with meningioma; its characteristic serious adverse effect is hepatotoxicity, and gynecomastia from aromatization is common but unrelated to meningioma.
Option C: Option C is incorrect; spironolactone is not associated with meningioma; its characteristic adverse effects are hyperkalemia, menstrual irregularity, and hypotension from mineralocorticoid receptor blockade.
Option E: Option E is incorrect; enzalutamide is not associated with meningioma; its distinctive CNS concern is seizure risk from GABA-A negative allosteric modulation, not meningioma formation.

16. Which of the following correctly distinguishes the physiological left ventricular hypertrophy of athletic training from the pathological left ventricular hypertrophy associated with anabolic-androgenic steroid (AAS) use?

A) Both athletic training and AAS use produce identical eccentric hypertrophy with enhanced diastolic function; there is no structural or functional difference between them.
B) Physiological athletic hypertrophy is typically eccentric (proportional increase in chamber volume and wall thickness) with preserved or enhanced diastolic function, whereas AAS-associated hypertrophy is typically pathological concentric hypertrophy (increased wall thickness with reduced or normal chamber volume) accompanied by reduced diastolic compliance and increased predisposition to arrhythmia.
C) Physiological athletic hypertrophy is concentric with impaired relaxation, while AAS-associated hypertrophy is eccentric with normal diastolic function.
D) AAS-associated hypertrophy is fully reversible within days of cessation and never associated with fibrosis, whereas physiological athletic hypertrophy is permanent and progressive.
E) Neither athletic training nor AAS use produces left ventricular hypertrophy; the echocardiographic changes seen in both are artifacts of measurement technique.

ANSWER: B

Rationale:

Option B is correct. Distinguishing physiological from pathological left ventricular hypertrophy (LVH) is clinically important in evaluating athletes and AAS users. Physiological hypertrophy from endurance and resistance training is typically eccentric — a proportional increase in chamber volume and wall thickness — and is accompanied by preserved or even enhanced diastolic function (normal or improved ventricular relaxation and filling). AAS-associated cardiac hypertrophy, by contrast, is typically pathological concentric hypertrophy, characterized by increased wall thickness with a normal or reduced chamber volume, reduced diastolic compliance, impaired relaxation, and an increased predisposition to both supraventricular and ventricular arrhythmias. AAS use is also associated with myocardial fibrosis and, in some cases, dilated cardiomyopathy, and the structural changes may not fully reverse after cessation.

Option A: Option A is incorrect; the two forms of hypertrophy are structurally and functionally distinct, not identical — this distinction is the core teaching point.
Option C: Option C is incorrect; it inverts the patterns — physiological athletic hypertrophy is eccentric with preserved diastolic function, and AAS hypertrophy is concentric with impaired relaxation.
Option D: Option D is incorrect; AAS-associated hypertrophy is not reliably reversible within days and is associated with myocardial fibrosis, while physiological athletic hypertrophy tends to regress with detraining rather than being permanent and progressive.
Option E: Option E is incorrect; both training and AAS use produce genuine, measurable left ventricular hypertrophy; the changes are real structural adaptations, not measurement artifacts.