[Abnormal hormone values: do drugs play a role? Abnormal prolactin, TSH and thyroid hormone values]

Whenever abnormal hormone values are found in a patient, it is necessary to inquire whether medicaments may be implicated. Some of the mechanisms of drug induced hormonal alterations are presented, and drugs which affect and alter prolactin, TSH, thyroid hormones and (in brief) GH and ACTH are summarized and discussed for the non-specialist. Hyperprolactinemia is caused by estrogens, neuroleptics and other dopaminantagonists, antidepressants, opioids, reserpine, a-methyl-dopa, H2-receptor blockers, etc. Serum TSH is decreased by glucocorticoids, somatostatin, dopaminergic agents, a-adrenergic blockers, etc., and increased by neuroleptics and other dopamin antagonists, cimetidine, clomiphene, spironolactone, etc. Thyroid hormones are altered by agents which inhibit thyroid hormone synthesis or secretion (thionamides, some sulfonamides; lithium), which increase (estrogens, methadon) or decrease (androgens, glucocorticoids) the concentration of TBG (thyroxine binding globulin), which competitively inhibit thyroid hormone binding to TBG (salicylates, phenytoin, etc.), and which inhibit the conversion of T4 to T3 (beta-adrenergic blockers, amiodarone, glucocorticoids) or stimulate degradation or fecal excretion of thyroid hormones (rifampicin, phenytoin, carbamazepine). For some drugs, in particular those with multiple effects on one or several endocrine systems, the only safe test which definitely allows drug-induced hormonal disturbances to be confirmed or ruled out is withdrawal of the drug and repetition of the hormone measurement.