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  • Title: Biphasic change in pituitary capacity induced by estrogen in hypogonadal women.
    Author: Lachelin GC, Yen SS.
    Journal: J Clin Endocrinol Metab; 1978 Mar; 46(3):369-73. PubMed ID: 109457.
    Abstract:
    5 healthy postmenopausal women aged 52-59 years with elevated gonadotropin levels and low estradiol (E2) (10+ or -1.5 pg/mol) concentrations volunteered for this study which measured changes in responses to pulses of luteinizing hormone-releasing factor (LHF) (10 mcg at 2-hour intervals 3 times) and thyroid-releasing factor (TRF) (200 mcg at 2-hour intervals 3 times) for luteinizing hormone (LH), follicle stimulating hormone (FSH), and prolactin (PL) before and during administration of a large dose of ethinyl estradiol (EE) (400 mcg/day) for 5 days. Responses to LRF and TRF stimulation on the 2nd and 5th days of EE treatment were studied in 2 experimental periods in the same individual at an interval of at least 10 weeks between treatments. During 5 days of EE treatment, LH 1st declined (50%) and then returned to the original level, forming a previously observed U-shaped curve. The initial fall in basal FSH level was not followed by a return to pretreatment level. These changes were accompanied by an exponential increase of more than 3-fold in the PL levels. The bidirectional pattern of LH release was associated with parallel changes in pituitary sensitivity to a 10-mcg pulse of LRF. Pituitary reserve, defined as the response to the 2nd and 3rd pulses of LRF, exhibited unidirectional augmentation. This progression in PL release upwards was unaccompanied by changes in pituitary PL sensitivity and reserve. The contribution of hypothalamic LRF and dopamine in the participation of these functional changes of LH, FSH, and PL are discussed.
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