Effect of cimetidine o endocrine functions--prolactin

Effects of cimetidine on the endocrine function were examined in 16 human subjects, i.e. 6 healthy adult volunteers, and each 5 male and female gastro-duodenal ulcer patients. They were all subjected to the examination on the fluctuation of prolactin (PRL) after one-shot intravenous injection of cimetidine. The peptic ulcer patients were orally given 800 mg/day of cimetidine for further 4 weeks. PRL, gonadotropins and sex hormones were determined in the male patients, and only PRL in the females patients. TRH-load test was carried out in all the ulcer patients before and after the administration of cimetidine. The results are shown below: 1) After one-shot intravenous administration of cimetidine 200 mg, serum-PRL significantly increased, the peak level, however, being within normal value range. The increase in PRL was transient, and recovered to the pretreatment value in 60-180 minutes after the administration. 2) During and after the repeated oral administration of 800 mg/day of cimetidine for the consecutive 28 days, serum PRL level did not significantly change. Neither was noted any influence on gonadotropin (LH, FSH) nor sex hormones (estradiol, testosterone) secretion. 3) PRL secretory functions at 500 microgram TRH loading were similar before and after oral administration of cimetidine, without difference in the reactivity.