Hypergonadotropic hypogonadism mainly is a testicular disorder with low testosterone levels despite high luteinizing hormone (LH) input. This occurs when the testes are not functionally normally, although the hypothalamus continues to release gonadotropin releasingn hormone (GnRH) and the pituitary secretes LH and follicle stimulating hormone (FSH) normally. Although the gonadotropins are signaling the testes, they are not capable of responding with increased secretion of sex steroids. In the case of prolactinemia, the hypothalamic effect results in inhibition of LH.
Hypogonadotropic hypogonadism can be either a primary pituitary disorder with low LH stimulus and low testosterone levels, or a primary hypothalamic disorder with decreased GnRH release resulting in both low LH and testosterone levels. In this case the testes function normally but the hypothalamic-pituitary functions are abnormal. Although the testes secrete sex steroids, there is no response elsewhere in the axis. Limbic discharges may affect the hypothalamic pulsatile release of GnRH. Decreased pulse frequency leading to diminished LH response and hypogonadism.
Androgen feedback control of LH and FSH includes a direct negative feedback at the hypothalamus and the pituitary by testosterone as well as dihydrotestosterone. Testosterone and estradiol can inhibit LH at the pituitary. The other testicular hormone, inhibin, has a direct negative feedback at the pituitary, where it inhibits FSH production and release. Testosterone is produced in the Leydig cells and inhibin is produced in the Sertoli cells of the testes.
Reviewed and revised September 2004 by Steven C. Schachter, MD and Orrin Devinsky MD, epilepsy.com Editorial Board.
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