Pituitary responsiveness to synthetic luteinizing hormone releasing hormone (LH-RH) during the menstrual cycle and in female hypogonadism.

The pituitary responsiveness to synthetic luteinizing hormone releasing hormone (LH-RH) in female patients with primary and secondary hypogonadism was tested and compared with that in normal women with regular menstrual cycles. A 200 mug dose of synthetic LH-RH was injected intravenously into 15 normal menstruating women, 8 patients with primary hypogonadism and 5 patients with secondary hypogonadism and the serum luteinizing hormone (LH) and follicle stimulating hormone (FSH) response to LH-RH was investigated using double-antibody radioimmunoassay. In normal women, the LH response to LH-RH in the preovulatory phase was greater than that seen in the follicular (p less than 0-05) and luteal phases (p less than 0-05) of the menstrual cycle. In contrast, no significant difference in the FSH response was demonstrated among the three different phases of the cycle. The serum LH response to LH-RH in primary hypogonadism was greater than that in the follicular (p less than 0-01) and luteal phases (p less than 0-01) of the cycle. The serum FSH response in primary hypogonadism was markedly greater than that in the follicular (p less than 0-01), preovulatory (p less than 0-01) and luteal phases (p less than 0-01) of the menstrual cycle. Conversely, the LH levels after LH-RH administration in secondary hypogonadism were significantly lower than in the follicular (p less than 0-01), preovulatory (p less than 0-01) and luteal phases (p less than 0-01) of the cycle. The FSH response in secondary hypogonadism was slightly below that in the follicular phase (p less than 0-05). Thus, the FSH response to LH-RH in primary hypogonadism and the LH response in secondary hypogonadism seemed to be sufficiently characteristic to have diagnostic value.