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Neurohypophyseal Hormones and Reproductive Hormone Secretion
Published in Craig A. Johnston, Charles D. Barnes, Brain-Gut Peptides and Reproductive Function, 2020
Very few studies have been performed specifically to examine the influence of OXY or AVP on FSH secretion. Oftentimes, LH secretion has been used as the endpoint in evaluating effects on gonadotropin secretion despite the fact that increasing evidence suggests that a specific FSH-releasing factor, separate from LHRH, may exist and, therefore, FSH could easily undergo differential control from LH secretion. In light of the explosive discovery of physiological effects for activin and inhibin, and the differential effects which these peptides appear to produce on LH and FSH secretion, as well as the recent findings emerging which demonstrate a differential ability of activin to influence AVP and OXY synthesis and release, a more careful evaluation of the influence which OXY and/or AVP may exert on FSH secretion is warranted.
Ovarian and menstrual cycles
Published in David M. Luesley, Mark D. Kilby, Obstetrics & Gynaecology, 2016
The granulosa cells of the growing follicles secrete a group of proteins which are important for regulating the HPO axis. In the early follicular phase FSH induces granulosa cells to secrete activin and inhibin A. Activin augments FSH action by increasing its receptors and up-regulates granulosa cell proliferation and aromatase enzyme production. Activin also inhibits the theca cells, androgen production.
The Pathophysiology of Male Infertility
Published in Botros Rizk, Ashok Agarwal, Edmund S. Sabanegh, Male Infertility in Reproductive Medicine, 2019
Sertoli cells, supportive cells present in the epithelium of the seminiferous tubules, are critical players in spermatogenesis, providing nourishment, physical support, and hormonal signals required for successful spermatogenesis. Sertoli cells support the germ cells through the developing stages. They have FSH receptors that enable FSH to act upon them for progression of spermatogenesis. They also produce vital hormones, activin, and inhibin, which mediate the feedback regulations of hypothalamic GnRH and pituitary gonadotropins. These LH and FSH in turn determine the testosterone production by the Leydig cells and initiation of spermatogenesis via acting on Sertoli cells, respectively [28]. Therefore, Sertoli cells and their ability to support spermatogenesis act as a limiting factor for spermatogonial proliferation [29]. Disruption of Sertoli cell function leads to irreversible testicular atrophy [30]. Sertoli cell toxicants are more severe than germ cell toxicants because the latter fails to deplete the entire stem cell mass, and the damage caused are thus reversible with the seminiferous tubules repopulating the germinal epithelium with due period [31]. Disruptors or toxicants may induce morphological defects by vacuolation of the cytoplasm and shedding of apical germ cells [30]. Seminiferous tubule fluid (STF), secreted by the Sertoli cells, is responsible for the required nutritional and hormonal microenvironment for normal spermatogenesis, and STF may also be depleted following exposures to toxicants or testicular injury, which precedes bulk necrosis of the germ cells [32]. Decrease or prevention in production of proteins inhibin B and androgen-binding protein (ABP) by the Sertoli cells have also been documented that link to depletion of specific spermatogonia [33,34]. For this association, serum inhibin B measurement serves as a noninvasive means of the assessment of male fertility [35].
Re-determination of upper reference range of follicular stimulating hormone in infertile men
Published in Systems Biology in Reproductive Medicine, 2020
Muharrem Ozkaya, Unal Oztekin, Mehmet Caniklioglu, Oguz Ekmekcioglu
Follicular Stimulating Hormone (FSH) which is released with the stimulation of Gonadotropin-releasing Hormone (GnRH) and other factors, and whose secretion is modulated by glycoproteins such as Activin and Inhibin, is a peptide-structured hormone. It is secreted from the anterior part of the pituitary gland. FSH indicates the ability to produce sperm as a result of the feedback mechanism in the hypothalamic-pituitary-gonadal axis (HPGA) (Nieschlag et al. 1999; Tsutsui et al. 2010). Though the diurnal variability of FSH, a single serum FSH measurement shows the expected FSH value with great reliability. Hormonal assessment is also recommended as a part of the full evaluation in infertility. A high FSH level is an indicator of abnormal spermatogenesis and testicular insufficiency (Jarow et al. 2010).