Gonadal hormones ovarian

The influence of gonadal hormones on prepubertal animals suggests some steroidal sensitivity in adults with regard to F. elicitation. Young male sheep are induced to perform F. in response to exogenous T and to 17-p-estradiol F. in female red deer is also sensitive to T injections (Parrott, 1978 Fletcher, 1978). Sex differences can interact with the hormonal state where social conditions vary. Female cats (intact) display F. to urine marks only in the absence of males testosterone propionate induced F. in spayed females towards estrous females (Verbeme, 1976 Hart and Leedy, 1987), whereas an ovarian hormone (estradiol) failed to elicit F. to males (intact, and sexually inactive), presumably indicative of social inhibition overriding steroid facilitation. 

The HPG axis is responsible for the cyclic hormone secretion that regulates and controls ovulation and plays a major role in menstruation-related disorders. The menstrual cycle is characterized by cyclic alterations in the production of gonadal hormones (estradiol and progesterone), pituitary hormones (gonadatropins, prolactin, growth hormone), melatonin, and cortisol and in temperature rhythms. Menstruation-related disorders are likely the result of a complex interaction between ovarian steroids and central neurotransmitters, neurohormones, and neuropeptides. The occurrence of physical... 

The steroid hormones, derived from cholesterol, include the adrenal cortical hormones (e.g., cortisol, aldosterone, and the adrenal sex steroids dehy-droepiandrosterone [DHEA] and androstenedione) and the gonadal hormones (e.g., the ovarian and testicular sex steroids, such as testosterone and estrogen). 

Disappearance of the negative feedback control of hormones leads to uncontrolled hormone secretion. For example, ovarian failure—as it happens in menopause—is caused by the luteinizing hormone and follicle-stimulating hormone levels increase due to the lack of negative feedback effects of the gonadal hormones. 

Two protein hormones, inhibin and activin, have been identified in gonadal tissue. Inhibin has been isolated from ovarian foUicular fluid and found to inhibit pituitary secretion of FSH. Inhibin is a glyocoprotein heterodimer consisting of two disulfide-linked subunits, a and P two types of P-subunit,... 

Ovarian hormones influence fluid intake by interaction with the brain renin-angiotensin system and it has been shown that gonadal steroids affect brain fluid-electrolyte balance by interactions with vasopressin. Both hyperos-molarity and increased intracranial pressure stimulate vasopressin release and intraperitoneal administration of vasopressin antagonists decrease brain volume. 

Cyclophosphamide and vincristine are examples of alkylating agents capable of inducing gonadal dysfunction. Premature menopause is a primary outcome of exposure to these agents. Amenorrhea and abnormal hormonal levels are characteristics of the ovarian dysfunction induced by cyclophosphamide. 

Inhibin, an ovarian protein hormone, has been shown to selectively decrease FSH but not LH secretion by the anterior pituitary cell. The gonadal source of inhibin has been localized to the testis Sertoli cells [76] and ovarian granulosa [77]. In cultured granulosa cells, FSH increases inhibin production via stimulation of the protein kinase A pathway. In vivo treatment with injections of gonadotropin also increases the circulating levels of inhibin [78], whereas treatment with inhibin... 

Inhibin B is produced by the developing follicles, and concentrations peak during the follicular phase. Concentrations of inhibin B have been used in conjunction with serum FSH and estradiol to assess ovarian function. Because inhibin is produced by gonadal tissue, it is thought to be a more direct marker of gonadal activity and ovarian reserve than pituitary hormones. In addition, cycle day 3 inhibin B concentrations may demonstrate a decrease before day 3 FSH concentrations. ... 

---