The effects of bromocriptine on the pulsatile pattern and the circadian profile of gonadotropins and testosterone secretion in normal adult men

Abstract

To investigate the effects of bromocriptine on the secretion mechanism of pituitary gonadotropins and testosterone, 5 mg of bromocriptine was administered to five young adult men who were normal in their endocrinological states. Blood samplings were taken from two hours before until six hours after the administration every 15 min., and after that, blood samplings were continued until 21 hours every one hour by an intravenous indwelling catheter. Serum FSH, LH, prolactin and testosterone levels were determined by RIA, and the changes of the pulsatile patterns of FSH and LH, and the circadian profile of these hormones by the administration of bromocriptine were analysed. Serum prolactin levels decreased significantly (p less than 0.005) from two hours after the administration of bromocriptine and remained in a very low range until the end of the experiment. The basal levels of FSH showed a significant decrease from two to six hours after the administration (p less than 0.005). Also the basal levels of LH showed a significant decrease from two to six hours after the administration (p less than 0.005). However, the basal levels of serum FSH and LH did not show significant decreases after that until the end of the experiment. No significant change was observed in the amplitude or the frequency of the pulsatile patterns of FSH and LH until six hours after the administration of bromocriptine. The serum levels of testosterone were also significantly decreased from two to six hours after the administration (p less than 0.005), but they did not show a significant decrease after that until the end of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)