Pituitary gonadotrophin responsiveness to synthetic LRF in subjects with normal and abnormal hypothalamic-pituitary-gonadal axis.

Abstract

Pituitary gonadotropin responsiveness to synthetic LRF was studied in normal males, in normal females at different phases of the menstrual cycle, in premenopausal females treated with synthetic estrogen, and in subjects with various abnormalities of the hypothalamic-pituitary-gonadal axis. Iv injection of from 1 to 450 mcg LRF in normal males resulted in an increase of luteinizing hormone (LH) within 2 minutes, with a maximal concentration of LH at a median time of 25 minutes. Maximal follicle stimulating hormone (FSH) levels occurred at a median time of 45 minutes. LH, and to a lesser extent FSH, increased with dose, although a wide variation in quantitative response to the same dose of LRF was seen among patients. In female subjects, the response to LRF varied during different phases of the menstrual cycle. The most sensitive period for pituitary response to LRF for both LH and FSH was just prior to the midcycle surge. Chronic estrogen treatment of premenopausal women enhanced pituitary responsiveness to LRF, with an alteration in both time and magnitude of response. Altered pituitary responsiveness was seen in patients with gonadal dysgenesis, hypogonadotropism, hypogonadotropic hypothalamic amenorrhea, panhypopituitarism, and pituitary tumor.