Effects of a dopamine antagonist (metoclopramide) on the release of LH, FSH, TSH and PRL in normal women throughout the menstrual cycle.

To obtain further insight into the role of endogenous dopamine on the adenohypophyseal hormones secretion in normal women, responses of the adenohypophyseal hormones to a dopamine antagonist, metoclopramide, were evaluated in 7 normal women during the early follicular, late follicular and mid-luteal phases of the menstrual cycle. PRL increments following metoclopramide were similar in all phases. During the early and late follicular phases, metoclopramide induced no significant change in circulating LH levels. However, a significant rise in serum LH was observed following metoclopramide during the mid-luteal phase. No significant changes in serum FSH levels were observed after metoclopramide during any of the 3 phases of the cycle. Following metoclopramide, serum TSH levels significantly rose in all phases. TSH increments following metoclopramide were significantly lower in the mid-luteal phase than in the early follicular phase. These results suggest that the modulatory effect of endogenous dopamine on adenohypophyseal hormones secretion is variable and selective throughout the normal menstrual cycle.