Variation in Lh and FSH Response to Lh‐releasing Hormone During the Menstrual Cycle

Abstract

Summary Synthetic luteinizing hormone‐releasing hormone (LRH) was injected intravenously in a dose of 100 μg. to test the capacity of the pituitary to respond to LRH with a release of luteinizing hormone (LH) and follicle‐stimulating hormone (FSH) in 16 healthy regularly menstruating women. A total of 28 LRH tests were performed during different stages of the menstrual cycle. Venous blood was obtained before and at frequent intervals during the first two hours after the LRH injection and assayed for LH, FSH and in five tests also for thyrotrophic (TSH) and growth hormone (GH). No consistent change of TSH or GH was observed after LRH. In all the 28 LRH tests there was a significant increase of LH and in tests also of FSH. The mean LH and FSH increase was 292 and 40 per cent, respectively. The maximum response was usually observed after 30 to 45 minutes. There was a pronounced variation in the response to LRH in the course of the menstrual cycle. During the late follicular phase the average LH response was 4‐ to 6‐fold that obtained in the early and mid‐follicular phase. An increased pituitary responsiveness was also found in the luteal phase. It was suggested that this variation in the response to LRH is due to the changes of the ovarian secretion of oestrogens during the menstrual cycle. In one amenorrhoeic woman exogenous oestrogen was found to enhance the LH response to LRH.

Sodium Valproate-Induced Menstrual Disturbance in Young Women

“…whilst a second group with low oestrogen excre tion had small responses. These data indicate that there is a relationship between oestrogens and the LH response to GnRH and this is confirmed by the finding that pretreatment with oestrogens enhances the LH response to GnRH [13]. Furthermore, oestrogens increase the num ber and sensitivity of pituitary GnRH receptors in rats and monkeys [14][15][16].…”

Effect of Ovariectomy and Estradiol Benzoate Treatment on LH-RH Induced LH and FSH Release in the Female Rabbit

“…In humans too, an enhanced pituitary responsiveness to LH-RH was found during phases of the menstrual cycle when estrogen levels are high (Yen et al, 1974;Nillius and Wide, 1972; and in eugonadal women (Jaffe and Keyes, 1974) and postmenopausal women treated with adequate amounts of exogenous estrogen for suffi cient time.…”

Direct evidence of estrogen modulation of pituitary sensitivity to luteinizing hormone-releasing factor during the menstrual cycle.

“…hanced pituitary responsiveness to LRF was found during the high-estrogen phase of the menstrual cycle (2,3) and in subjects without ovarian function (4). On the other hand, estrogen administration to levels equivalent to those found at midcycle reduces the pituitary responsiveness to LRF in humans (5,6) as well as in monkeys (7).…”