Gonadotropin response to luteinizing hormone releasing hormone in hyperthyroid patients with menstrual disturbances.
This study was designed to investigate the gonadotropin response to luteinizing hormone releasing hormone (LHRH) in patients with hyperthyroidism, as related to the presence or absence of menstrual disorders. Forty-one Japanese women with hyperthyroidism were separated into groups on the basis of the presence of a regular menstrual cycle, hypomenorrhea, or amenorrhea and further subdivided into the phase of the menstrual cycle at the time of testing. The findings in these groups were compared with those in normal subjects with respect to thyroid function, basal serum LH and FSH levels and serum LH and FSH responses to LHRH, and basal estradiol levels. Serum LH responses to LHRH were increased over normal subjects in those with hyperthyroidism regardless of the phase of the menstrual cycle and regardless of the presence or absence of menstrual disturbances. However, these augmented LH responses to LHRH were less marked in those with menstrual disorders than in those with regular menstruation. Both basal serum FSH and peak serum FSH response to LHRH were also increased in the follicular phase but not in the luteal phase of the cycle in hyperthyroid patients, regardless of menstrual function. These results suggest that high levels of circulating thyroid hormones augment the gonadotropin response to LHRH, and that increased LH and FSH secretion probably maintains the normal cyclic pituitary gonadal axis function in patients with hyperthyroidism.