Penile erection occurs when blood swells the corpus cavernosum, an effect facilitated by relaxation of regional smooth muscle. Smooth muscle tone is regulated by cellular Ca2+, which activates the Ca2+/calmodulin (CaM)-dependent enzyme myosin light chain kinase (MLCK), which leads to MLC phosphorylation and contraction. The nitric oxide (NO) pathway leads to relaxation of smooth muscle by stimulating the soluble guanylyl cyclase (sGC), which results in the production of cyclic GMP (cGMP) and the activation of cGMP-dependent protein kinase (PKG). PKG causes smooth-muscle relaxation by mechanisms that are still being defined and that might include a reduction in cytosolic Ca2+ (by enhanced Ca2+ export and/or by reduced inositol trisphosphate (InsP3) receptor-mediated Ca2+ mobilization) and dephosphorylation of myosin light chains (by activation of MLC phosphatase and/or by sequestration of MLCK in a phosphorylated form that is not readily activated by Ca2+/CaM). Viagra® specifically inhibits the breakdown of cellular cGMP by PDE5 (an isoform of phosphodiesterase that is localized to erectile tissue), and thereby prolongs and enhances the effects of NO/cGMP.
- not a product of the ovary, estriol is the predominant urinary end product of estrogen metabolism. In the pregnant woman, estriol, as estradiol and estrone, are secreted by the placenta. Displays minimal estrogenic activity.
Increased NO. PGI2 synthesis – hyperinsulinemia prevention by estrogen
Perform a clomiphene challenge test , which is sometimes used to evaluate a woman's ovulation and egg quality ( ovarian reserve ). When given early in a woman's menstrual cycle for 5 days, clomiphene elevates a woman's follicle-stimulating hormone (FSH) level. On the next day, an FSH blood level that has dropped back to normal is a sign of a normal ovarian reserve and ovulation. An elevated FSH is a sign of low ovarian reserve. Women with a diminished ovarian reserve can use donor eggs, which greatly improves their chances of giving birth to a healthy child.
Progesterone acts as a Brain anaesthetic. Increase MAO concentration thus producing depression and irritability
Androgens, Oestrogens, Progestins and Hormonal Contraceptives Department of Pharmacology NEIGRIHMS, Shillong