Adrenocorticosteroid Pharmacology

Correct Answer

B — Metyrapone

Rationale

Metyrapone is classified as a CYP11B1 (11-beta-hydroxylase) inhibitor. CYP11B1 catalyzes the final step in cortisol synthesis — conversion of 11-deoxycortisol to cortisol. Fludrocortisone is a mineralocorticoid receptor agonist. Spironolactone and finerenone are mineralocorticoid receptor antagonists.

Correct Answer

A — Fludrocortisone

Rationale

Fludrocortisone is classified as a mineralocorticoid receptor agonist — the only oral mineralocorticoid replacement agent in clinical use. Spironolactone, eplerenone, and finerenone are all mineralocorticoid receptor antagonists used in heart failure, primary hyperaldosteronism, and diabetic kidney disease.

Correct Answer

C — Prednisone

Rationale

Prednisone is classified as a prodrug: it is pharmacologically inactive as administered and requires hepatic conversion by 11-beta-hydroxysteroid dehydrogenase type 1 to prednisolone, its active form. Hydrocortisone, dexamethasone, and budesonide are active as administered and do not require hepatic conversion for activity.

Correct Answer

D — Dexamethasone

Rationale

Dexamethasone is classified as a long-biologic-duration glucocorticoid, with a biologic half-life of 36 to 54 hours — the longest among commonly used agents. Hydrocortisone is short-duration (8 to 12 hours). Prednisone and prednisolone are intermediate (18 to 36 hours). Triamcinolone is intermediate to long (24 to 48 hours in tissues), but dexamethasone represents the long-duration class anchor.

Correct Answer

A — Spironolactone

Rationale

Spironolactone is classified as a steroidal mineralocorticoid receptor antagonist. Its steroidal structure accounts for off-target activity at androgen and progesterone receptors, producing gynecomastia and sexual side effects. Finerenone is a non-steroidal mineralocorticoid receptor antagonist. Fludrocortisone is a mineralocorticoid receptor agonist. Metyrapone is a steroidogenesis inhibitor (CYP11B1 inhibitor), not a receptor antagonist.

Correct Answer

C — Finerenone

Rationale

Finerenone is the only non-steroidal mineralocorticoid receptor antagonist among these options. Its non-steroidal structure confers high mineralocorticoid receptor selectivity without off-target androgen or progesterone receptor activity, distinguishing it from the steroidal antagonists spironolactone and eplerenone. Fludrocortisone is a mineralocorticoid receptor agonist, not an antagonist.

Correct Answer

B — Transactivation of glucocorticoid response element-dependent genes drives adverse metabolic effects such as hyperglycemia and osteoporosis

Rationale

Glucocorticoid receptor homodimers bind glucocorticoid response elements and activate transcription of gluconeogenic enzymes, muscle ubiquitin ligases, and genes suppressing osteocalcin synthesis — producing hyperglycemia, muscle atrophy, and osteoporosis through transactivation. The anti-inflammatory effects (cyclooxygenase-2 suppression, interleukin inhibition) are driven by tethered transrepression, in which glucocorticoid receptor monomers physically bind and inhibit nuclear factor kappa-B and activator protein-1 without requiring glucocorticoid response element binding. Transrepression does not drive metabolic adverse effects.

Correct Answer

A — Glucocorticoids induce annexin-A1, which inhibits phospholipase A2 and reduces arachidonic acid availability for both cyclooxygenase and lipoxygenase pathways

Rationale

Glucocorticoids induce annexin-A1 (lipocortin-1), an endogenous inhibitor of cytosolic phospholipase A2. Because phospholipase A2 releases arachidonic acid from membrane phospholipids — the shared substrate for both cyclooxygenase (producing prostaglandins and thromboxanes) and lipoxygenase (producing leukotrienes) — annexin-A1 induction suppresses eicosanoid synthesis at an upstream point that affects all downstream products. Nonsteroidal anti-inflammatory drugs block only cyclooxygenase, leaving the lipoxygenase pathway intact and leukotrienes unaffected.

Correct Answer

D — Glucocorticoids suppress adhesion molecule expression, reducing neutrophil margination, and accelerate release of mature neutrophils from bone marrow storage pools

Rationale

Glucocorticoid-induced neutrophilia results from two redistribution mechanisms: suppression of L-selectin and Mac-1 expression on neutrophil surfaces reduces margination to the vascular endothelium, and accelerated release of mature neutrophils from bone marrow storage pools expands the circulating pool. Neutrophil proliferation is not stimulated. Antimicrobial function is not enhanced — an elevated neutrophil count in a steroid-treated patient cannot be used as a reliable indicator of bacterial infection.

Correct Answer

C — Glucocorticoids impair insulin-stimulated GLUT4 translocation to the plasma membrane in skeletal muscle and adipose tissue

Rationale

In skeletal muscle and adipose tissue, glucocorticoids reduce glucose transporter type 4 (GLUT4) translocation to the plasma membrane in response to insulin, impairing insulin-stimulated glucose uptake independently of changes in circulating insulin concentration. This peripheral insulin resistance, combined with hepatic upregulation of gluconeogenic enzymes (phosphoenolpyruvate carboxykinase and glucose-6-phosphatase), produces the characteristic pattern of glucocorticoid-induced hyperglycemia. Glucocorticoids do not primarily act through glucagon stimulation, direct beta cell suppression, or renal glucose reabsorption.

Correct Answer

B — Steroid myopathy results from proteasomal degradation of myofibrillar proteins without inflammatory muscle injury, so membrane integrity is preserved and creatine kinase release is minimal

Rationale

Steroid myopathy arises from glucocorticoid receptor-dependent upregulation of ubiquitin ligases (MuRF1 and MAFbx), which target myofibrillar proteins for proteasomal degradation and suppress muscle protein synthesis. Because this atrophy occurs without inflammatory injury to muscle cell membranes, creatine kinase — which leaks from cells when membranes are disrupted — remains normal or only mildly elevated. This contrasts with inflammatory myositis, where immune-mediated muscle destruction causes markedly elevated creatine kinase. The distinction is clinically important: inflammatory myopathy is treated with increased glucocorticoids, while steroid myopathy requires dose reduction.

Correct Answer

A — Glucocorticoids increase RANKL expression and decrease osteoprotegerin, shifting the balance toward osteoclast activation, while simultaneously suppressing osteoblast differentiation and promoting osteoblast apoptosis

Rationale

The primary cellular mechanism of glucocorticoid-induced osteoporosis involves a RANKL/osteoprotegerin imbalance: glucocorticoids upregulate RANKL (which activates osteoclasts) while downregulating osteoprotegerin (the decoy receptor that normally inhibits RANKL), promoting bone resorption. Simultaneously, glucocorticoids suppress osteoblast differentiation from precursor cells and induce apoptosis of mature osteoblasts, reducing bone formation. This dual mechanism — enhanced resorption and impaired formation — explains why fracture risk exceeds what bone mineral density alone predicts. Impaired intestinal calcium absorption and increased renal calcium loss are secondary contributors that worsen bone loss over time.

Correct Answer

D — The enzyme 11-beta-hydroxysteroid dehydrogenase type 2, co-expressed with the mineralocorticoid receptor in the distal nephron, converts cortisol to inactive cortisone before it can activate the receptor

Rationale

Cortisol binds the mineralocorticoid receptor with affinity equal to or greater than aldosterone. Selectivity is conferred not by receptor structure but by a prereceptor gating enzyme: 11-beta-hydroxysteroid dehydrogenase type 2 is co-expressed with the mineralocorticoid receptor in aldosterone-sensitive distal nephron cells and rapidly converts cortisol to cortisone, which cannot activate the receptor. Aldosterone is not a substrate for this enzyme and therefore escapes inactivation. When this gating mechanism is blocked — by glycyrrhizic acid from licorice or by high-dose glucocorticoid therapy saturating the enzyme — cortisol activates renal mineralocorticoid receptors, producing hypertension and hypokalemia (apparent mineralocorticoid excess).

Correct Answer

C — Sustained exogenous glucocorticoid suppresses hypothalamic corticotropin-releasing hormone and pituitary adrenocorticotropic hormone secretion, causing the adrenal cortex to atrophy and lose capacity to produce cortisol independently

Rationale

Exogenous glucocorticoids suppress the hypothalamic-pituitary-adrenal axis through negative feedback: corticotropin-releasing hormone from the hypothalamus and adrenocorticotropic hormone from the pituitary are both suppressed. Without adrenocorticotropic hormone stimulation, the zona fasciculata atrophies. When the exogenous drug is abruptly withdrawn, the suppressed axis cannot recover immediately, and the atrophied adrenal cortex cannot produce sufficient cortisol — producing iatrogenic secondary adrenal insufficiency. Recovery of full axis function requires weeks to months depending on dose and duration. Tapering allows gradual axis recovery.

Correct Answer

B — Glucocorticoid receptor-dependent upregulation of ubiquitin ligases that target myofibrillar proteins for proteasomal degradation

Rationale

This patient has steroid myopathy. The normal creatine kinase is the key distinguishing feature: inflammatory myositis causes membrane disruption and markedly elevated creatine kinase, while steroid myopathy results from glucocorticoid receptor-mediated upregulation of ubiquitin ligases (MuRF1 and MAFbx) that degrade myofibrillar proteins through the proteasomal pathway without inflammatory injury. Muscle cell membranes remain intact, and creatine kinase does not leak. The clinical implication is critical: this condition requires prednisone dose reduction, not escalation.

Correct Answer

A — Fludrocortisone, because destruction of all three adrenocortical zones in primary adrenal insufficiency eliminates aldosterone production, requiring dedicated mineralocorticoid replacement

Rationale

Autoimmune adrenalitis destroys all three cortical zones, including the zona glomerulosa responsible for aldosterone synthesis. Hydrocortisone replaces glucocorticoid function but has insufficient mineralocorticoid potency at replacement doses to maintain sodium homeostasis. The resulting aldosterone deficiency produces sodium wasting, hyponatremia, hyperkalemia, and postural hypotension — as seen in this patient. Fludrocortisone (50 to 200 micrograms per day) provides the mineralocorticoid replacement. This requirement distinguishes primary adrenal insufficiency from secondary adrenal insufficiency, where the zona glomerulosa remains intact and responsive to the renin-angiotensin-aldosterone system.

Correct Answer

C — Glycyrrhizic acid in licorice inhibits 11-beta-hydroxysteroid dehydrogenase type 2, allowing cortisol to accumulate in distal nephron cells and activate mineralocorticoid receptors

Rationale

Glycyrrhizic acid, the active compound in licorice, inhibits 11-beta-hydroxysteroid dehydrogenase type 2 — the enzyme that normally converts cortisol to inactive cortisone in aldosterone-sensitive distal nephron cells. When this gating enzyme is blocked, cortisol accumulates in the distal nephron and activates mineralocorticoid receptors, driving sodium retention, potassium wasting, hypertension, and hypokalemia. Because this is cortisol acting on the mineralocorticoid receptor rather than increased aldosterone secretion, plasma renin and aldosterone are both suppressed — the hallmark of apparent mineralocorticoid excess. Aldosterone is not elevated and renin-angiotensin system activation is not the mechanism.

Correct Answer

D — Prednisone reduces neutrophil surface adhesion molecule expression and promotes release of neutrophils from bone marrow storage pools, raising circulating counts through redistribution rather than enhanced antimicrobial response

Rationale

Glucocorticoid-induced neutrophilia is a redistribution phenomenon, not a proliferative or functional response. Prednisone suppresses L-selectin and Mac-1 expression on neutrophil surfaces, reducing margination to the vascular endothelium, and accelerates release of mature neutrophils from bone marrow storage pools — both effects increase the circulating neutrophil count without enhancing antimicrobial killing capacity. Because this neutrophilia reflects pharmacological redistribution rather than an infectious stimulus, it cannot be interpreted as evidence of bacterial infection. Clinicians must rely on other markers (procalcitonin, cultures, clinical context) when evaluating for infection in steroid-treated patients.