STEROID

Biosynthesis Steroids Hormones

PRODUCTION LINE OF CHOLESTEROL and STEROIDS The raw material of steroid hormones is cholesterol. All steroid-producing organs (except placenta) can synthesize steroids from acetate, but most organs can not meet the needs of raw materials locally and require cholesterol in circulation. Major cholesterol carrier in the circulation is LDL - low density lipoprotein. LDL is taken out of circulation by the cells - steroidogenic cells using cell surface receptors that can recognize specific proteins on the surface of LDL (Apoprotein). Once in the cell, cholesterol is transported through a series of enzymatic changes for steroid hormones produce the final product: • Progestins • Androgens • Estrogen • Glucocorticoids (sugar) • mineralocorticoid (salt) All steroid producing tissues using molecular precursors and enzymes with a common sequence. Network specifications generated by the specific enzyme in the series. For example: different gonads adrenal glands because the ovaries and testes do not produce the enzyme 21-hydroxylase or 11β-hydroxylase required to produce corticosteroids that the gonads (ovaries and testes) produce only progestin, androgen and estrogen alone. During the conversion of cholesterol to steroid metabolites, the number of atoms C (carbon) decreased gradually. Progestins have 21 molecules of carbon (C-21); androgen carbon 19 (C-19) and estrogen carbon 18 (C-18). Progestins are obligatory precursors for the production of androgens and estrogens, whereas androgens are obligatory precursors to produce estrogen. Once formed pregnenolone, steroid production may continue to one of two paths, via the progesterone or 17 α-OH pregnonolon LOCATION PRODUCTION

OVARIUM Produce steroids in the ovary occurs in two cell systems. Theca cells produce androgens. Androgens diffuses into the granulosa cells and converted into estrogen. Theca cells respond to LH by increasing the number of LDL receptors and then insert cholesterol into cells. The presence of LH also causes increased production of androgens. When androgens diffuse into granulosa cells, androgen metabolized by aromatase to estrogen. FSH triggers aromatase activity in granulosa cells thereby increasing the conversion of androgens to estrogens. TESTIS in the testis, predominantly androgen production in the Leydig cells under the influence of LH. Androgens enter the circulation directly or perform diffusion into Sertoli cells nearby. Sertoli cells will convert androgens to estrogen. The mechanism of steroid production in the testis similar to that occurring in the ovarium. GLAND ADRENAL ProdUCE sex hormones by the adrenal is largely a product of the biosynthesis of corticosteroids. Contributions to the adrenal sex steroid total circulating sex steroids are generally very small except in certain circumstances. Ovary post-menopausal women no longer produce steroid hormones in sufficient quantity so that adrenal androgen production is clinically more meaningful. During pregnancy, the placenta can not synthesize cholesterol from acetate resulting in the formation of cholesterol from adrenal androgen dependent on the mother and the fetus. Low cortisol levels provide feedback to improve the production of adrenal glucocorticoids. When there is deficiency of 21 - hydroxylase occur in the female fetus, the increased production of androgens will cause masculinization of the external genitalia, known as congenital adrenal hyperplasia syndrome. Similarly, differentiation and sexual development disorders in men may be caused by genetic defects in androgen production.