Nursing Pharmacology Chapter 32: Hypothalamic and Pituitary Hormones
Location: hypothalamus (and other brain regions)
TRH stimulation of thyrotropin:
Blocked by thyroxine
Enhanced by thyroxine deficiency
Plasma half-life: 4-5 minutes
Thyrotropin levels: high
Enhanced thyrotropin response to TRH
Thyrotropin serum levels: low (by sensitive TSH assay) or "inappropriately normal"
TSH often does not increase after TRH
Serum thyrotropin levels: normal or low
Thyrotropin response to TRH: normal or attenuated
Increased prolactin released by the pituitary
No effect on growth hormone or ACTH
Some pituitary tumors:
Release growth hormone in response to TRH (acromegaly).
Release ACTH in response to TRH (Cushing's disease).
Failure to release prolactin (prolactinoma).
Anterior pituitary hormone.
Thyroid function regulation involves stimulation of thyroxine and triiodothyronine production and release.
Consists of two peptides (A and B) with associated carbohydrate side chains
Source: Recombinant human TSH
TSH-b subunit provides thyroid specificity since TSH-a subunit is nearly identical to a subunit of FSH, LH, hCG.
Route of Administration:
Possible diagnostic use in a metastatic thyroid carcinoma.
Possibly effective therapeutic stimulation of radioactive iodine uptake for treatment of metastatic thyroid carcinoma.
Fitzgerald, P.A. and Klonoff, D.C. Hypothalamic and Pituitary Hormones, in Basic and Clinical Pharmacology, (Katzung, B. G., ed) Appleton-Lange, 1998, pp 603-618.
Primary Reference: Biller, Beverly M. K. and Daniels, Gilbert, H. Neuroendocrine Regulation and Diseases of the Anterior Pituitary and Hypothalamus, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, pp 1972-1998