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  • Title: The sequence of pituitary responses to synthetic luteinizing hormone releasing hormone (LH-RH) throughout the normal menstrual cycle.
    Author: Grimes EM, Thompson IE, Taymor ML.
    Journal: Acta Endocrinol (Copenh); 1975 Aug; 79(4):625-34. PubMed ID: 1098349.
    Abstract:
    Thirty-one ovulatory women between 20 and 33 years of age were given 150 mug of synthetic LH-RH during different phases of the menstrual cycle. Five patients were studied during the early follicular phase (days 4-7); 10 patients during the late follicular phase (days 9-12); 6 patients during the "LH Surge"; 5 patients during the early luteal phase (days 14-16); 3 patients during mid-luteal phase (days 17-21); and 2 patients during late luteal phase (days 22-27). Oestrogen, progesterone, FSH and LH levels were determined from 30 min prior to LH-RH administration to 90 min thereafter in all cases. LH response to LH-RH increased progressively during the follicular phase. Enhanced pituitary responsiveness to LH-RH occurred at mid-cycle for both LH and FSH and maximum LH responses occurred during the "LH Surge" and early luteal phase. LH responses during the mid and late luteal phases were similar to late follicular phase responses. There were no significant differences between FSH responses during the early follicular, late follicular, mid-luteal and late luteal phases. Maximum pituitary responsiveness appears to occur in a gonadal steroid milieu of high oestrogen levels in association with rising but low progesterone levels. Progesterone or a crucial oestrogen: progesterone ratio may in fact potentiate pituitary release of LH during the early stages of corpus luteum formation. Pituitary responsiveness to LH-RH correlates positively with basal LH and oestrogen levels during the menstrual cycle and with the oestrogen:progesterone ratio during the luteal phase. The effect of 150 mcg of luteinizing hormone-releasing hormone (LH-RH) on estrogen (E), progesterone (P), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) levels was studied in 31 ovulatory women at different stages throughout the normal menstrual cycle. Measurements were made from 30 minutes prior to LH-RH administration to 90 minutes after administration. LH responses during the late follicular phase were significantly greater than early follicular responses (p less than .001) and significantly less than early luteal phase levels (p less than .01). LH responses during the spontaneous LH surge were greater than late follicular phase levels (p less than .01) but not significantly greater than early luteal phase responses. Mid-luteal phase LH responses were less than early luteal phase responses (p less than .01) but not significantly greater than late follicular or late luteal phase responses. The LH response correlated positively with E levels (p less than .02), basal LH levels (p less than .01), and the E:P ratio during the midcycle and luteal phase (p less than .05). Differences in FSH responses during the early follicular, late follicular, mid-luteal, and late luteal phases were not significant. FSH responses during the LH surge and early luteal phase were significantly greater than early follicular, mid-luteal, and late luteal phase levels (p less than .01). Maximum pituitary response seems to occur when E levels are high and P levels are low and increasing. P, or the E:P ratio, may potentiate the release of pituitary LH during the early stages of corpus luteum development.
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