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  • Title: Modulation of pituitary response to hypothalamic releasing factors.
    Author: Jaffe RB, Keye WR.
    Journal: J Steroid Biochem; 1975 Jun; 6(6):1055-60. PubMed ID: 1100905.
    Abstract:
    The effects of estradiol-17beta and gonadotropin releasing hormone (GRH) on serum concentrations of follicle stimulating hormone (FSH) and luteinizing hormone (LH) were studied during the menstrual cycle in women, and the effects of GRH were studied during the puerperium. 1 group of patients received either intravenous infusions of estradiol for 12 hours in doses comparable to midcycle concentrtions (225pg/ml) or late follicular phase concentrations (150 pg/ml), or intravenous injections for 6 days, followed by a single intravenous injection of 50 mcg GRH. Infusion of estradiol markedly auppressed pituitary gonadotropin responsiveness to GRH, while the sequence of injections augmented both LA and FSH responsiveness to GRH. The results suggest that estradiol has, at least in part, a direct effect on the pituitary gland. The effect of estradiol may be dependent on the length of exposure of the hypothalamic-pituitary axis to estradiol and the concentrations of the hormone. The gonadotropin response was not augmented until estradiol had been administered at least 3 days prior to GRH administration. In the postpartum women, LH responses to GRH prior to the 5th week postpartum were less than during the early follicular phase. During the 2nd month, however, the gonadotropin responses were as much as 9 times those observed during the follicular phase. The FSH response was also similar, but required a shorter period of time; the responses being of the same magnitude by the 3rd week as those in the follicular phase. The results indicate that anovulation during the 1st month postpartum is, in part, the result of pituitary unresponsiveness to GRH, though anovulation in the 2nnd month may involve hypothalamic and/or ovarian factors, but not pituitary factors.
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