The effects of omeprazole on endocrine function in man

We have assessed the effect of omeprazole on various endocrine functions in man. Eight healthy subjects took 60 mg omeprazole or placebo daily for 1 week in a double-blind, randomized, cross-over study. On Day 7 basal concentrations of follicle-stimulating hormone (FSH), luteinising hormone (LH), prolactin, testosterone, thyroid-stimulating hormone (TSH), and serum thyroxine (T4) and tri-iodothyronine (T3) were measured, followed by the gonadotrophin response to luteinising hormone releasing hormone (LHRH) and the prolactin and TSH responses to thyrotrophin releasing hormone (TRH). There were no differences in basal or stimulated values between omeprazole and placebo. In a second study, a further 8 subjects were similarly treated, and on Day 7 serial measurements of cortisol and 11-deoxycortisol were made before and for 2.5 h after intravenous adrenocorticotrophin (ACTH). There were no differences in basal values or pattern of response to ACTH for either hormone. Omeprazole in clinical practice is unlikely to cause any significant interference in endocrine function.