EFFECTS OF THE H-2-RECEPTOR ANTAGONIST CIMETIDINE ON PITUITARY-HORMONES IN MAN

The effects of the histamine (H2) receptor antagonist cimetidine on serum levels of prolactin (PRL), growth hormone (GH), thyroid stimulating hormone (TSH), luteinizing hormone (LH), follicle stimulating hormone (FSH) and cortisol were studied in 5 normal males. Cimetidine, when given by infusion at the dose of 100 mg/h for 5 h, did not alter adenohypophyseal secretion basally or after pituitary stimulation with LHRH [LH releasing hormone] and TRH [TSH releasing hormone]. However, 400 mg cimetidine given i.v. as a bolus injection significantly stimulated PRL release in all subjects, without affecting any other measured hormone. A dose-response relationship existed, and 200 mg cimetidine seems to be the minimum PRL-releasing dose when given as an i.v. bolus injection. Cimetidine apparently releases PRL and this effect is dose-related, but only when large i.v. injections are given.