Abstract
Estradiol secreted by growing ovarian follicle(s) has been considered classically to be the neural trigger for the preovulatory surge of gonadotropins. The observation that the estradiol-induced gonadotropin surge in ovariectomized rats is of lesser magnitude and duration than that found in the cycling rat at proestrus has resulted in a search for other steroid regulators. Progesterone is a major regulator of the preovulatory gonadotropin surge. It can only act in the presence of an estrogen background, which is necessary for the synthesis of progesterone receptors. In the estrogen-primed ovariectomized rat, progesterone is able to initiate and enhance the gonadotropin surge to the magnitude observed on the day of proestrus and limit it to 1 day. The physiological role of progesterone in the induction of the preovulatory gonadotropin surge has been demonstrated by the attenuation of the progesterone-induced surge and the endogenous proestrus surge by progesterone receptor antagonist RU486 and the progesterone synthesis inhibitor trilostane. The promoter region of the follicle-stimulating hormone (FSH)-β gene contains multiple progesterone response elements and progesterone brings about FSH release as well. The reduction of progesterone in the 5α-position appears to be important for the regulation of progesterone secretion. Corticosteroids appear to play a significant role in the secondary FSH surge on late proestrus and early estrus.
Original language | English (US) |
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Pages (from-to) | 616-629 |
Number of pages | 14 |
Journal | Steroids |
Volume | 63 |
Issue number | 12 |
DOIs | |
State | Published - Dec 1998 |
Keywords
- FSH
- GnRH
- Gonadotropin surge
- Hypothalamus
- LH
- Pituitary
- Steroid
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Endocrinology
- Pharmacology
- Clinical Biochemistry
- Organic Chemistry