Assessment of pituitary gonadotropin reserve using luteinizing hormone-releasing hormone (LRH) in states of altered thyroid function.

Menstrual irregularities commonly accompany hyper- and hypofunction of the thyroid gland. Investigation of the pituitary-ovarian axis was undertaken in 14 hyperthyroid and 8 hypothyroid patients. The pituitary luteinizing hormone (LH) and follicle stimulating hormone (FSH) responses to 100 mug luteinizing hormone-releasing hormone (LRH) was assessed. These responses were found to be similar to matched control groups in hyperthyroid premenopausal women with and without menstrual disturbances and in hyperthyroid men. The postmenopausal hyperthyroid women had an exaggerated LH response, although the FSH response was comparable to that of the control group. These results indicate normal pituitary LH and FSH reserve in hyperthyroidism. In hypothyroidism a gradation of gonadotropin response to LRH was found. In 2 of the patients there was an inadequate LH response in the presence of a normal FSH response. This demonstrates that in some cases of primary hypothyroidism there is limited pituitary LH reserve.