4337 Testosterone Testosterone is the most important androgen in potency and quantity•_Оa steroid sex hormone found in both men and women. Testosterone is synthesized and released by the Leydig cells that lie between the tubules and comprise less than 5% of the total testicular volume. testosterone diffuses into the seminiferous tubules where it is essential for maintaining spermatogenesis. Some binds to an androgen-binding protein (ABP) that is produced by the Sertoli cells and is homologous to the sex-hormone binding globulin that transports testosterone in the general circulation. The ABP carries testosterone in the testicular fluid where it maintains the activity of the accessory sex glands and may also help to retain testosterone within the tubule and bind excess free hormone. Some testosterone is converted to estradiol by Sertoli cell-derived aromatase enzyme. Leydig cell steroidogenesis is controlled primarily by luteinizing hormone with negative feedback of testosterone on the hypothalamic-pituitary axis. The requirement of spermatogenesis for high local concentrations of testosterone means that loss of androgen production is likely to be accompanied by loss of spermatogenesis. Indeed, if testicular androgen production is inhibited by the administration of exogenous androgens then spermatogenesis ceases. This is the basis of using exogenous testosterone as a male contraceptive. testosterone is converted to dihydrotestosterone by 5a-reductase type 2 (EC 1.3.1.22, SRD5A2), the androgen with the highest affinity for the androgen receptor. SRD5A2 deficiency illustrates the importance of dihydrotestosterone for external virilization, as individuals with this condition have normal male internal structures but their external genitalia are of female appearance. There is now clear evidence that the human fetal testis and also the fetal adrenal gland is capable of testosterone biosynthesis during the first trimester. Regardless of the source of androgen production, the target tissue responds by male sexual differentiation of the external genitalia by the end of the first trimester. It is clear that testicular damage may result in loss of testosterone production or the loss of spermatogenesis or both. Loss of androgen production results in hypogonadism, the symptoms of which reflect the functions of testosterone. Male hypogonadism is defined as failure of the testes to produce normal amounts of testosterone, combined with signs and symptoms of androgen deficiency. Systemic testosterone levels fall by about 1% each year in men. Therefore, with increasing longevity and the aging of the population, the number of older men with testosterone deficiency will increase substantially over the next several decades. Serum testosterone levels decrease progressively in aging men, but the rate and magnitude of decrease vary considerably. Approximately 1% of healthy young men have total serum testosterone levels below normal; in contrast, approximately 20% of healthy men over age 60 years have serum testosterone levels below normal. (A3376, A3377). In men, testosterone is produced primarily by the Leydig (interstitial) cells of the testes when stimulated by luteinizing hormone (LH). It functions to stimulate spermatogenesis, promote physical and functional maturation of spermatozoa, maintain accessory organs of the male reproductive tract, support development of secondary sexual characteristics, stimulate growth and metabolism throughout the body and influence brain development by stimulating sexual behaviors and sexual drive. In women, testosterone is produced by the ovaries (25%), adrenals (25%) and via peripheral conversion from androstenedione (50%). Testerone in women functions to maintain libido and general wellbeing. Testosterone exerts a negative feedback mechanism on pituitary release of LH and follicle-stimulating hormone (FSH). Testosterone may be further converted to dihydrotestosterone or estradiol depending on the tissue 58-22-0 6013 C19H28O2 White powder. 155°C 23.4 mg/L (at 25°C) Endogenous, Injection Testosterone is considered an anabolic steroid. It plays a key role in the development of male reproductive tissues such as the testis and prostate as well as promoting secondary sexual characteristics such as increased muscle, bone mass, and the growth of body hair. High levels of testosterone can lead to masculinization in females or premature puberty in young boys. Chronically high levels in adults increase the incidence of heart attack, stroke and blood clots by lowering the level of HDL (good cholesterol) and increasing the level of LDL (bad cholesterol). Chronic high use of anabolic steroids (such as testosterone) appears to lead to cardiac myopathy and weakening the left ventricle. The development of breast tissue in males, a condition called gynecomastia (which is usually caused by high levels of circulating estradiol), arises because of increased conversion of testosterone to estradiol by the enzyme aromatase. Reduced sexual function and temporary infertility can also occur in males. The mechanism of testosterone’s action is as follows: Free testosterone is transported into the cytoplasm of target tissue cells, where it can bind to the androgen receptor, or can be reduced to 5α-dihydrotestosterone (DHT) by the cytoplasmic enzyme 5-alpha reductase. DHT binds to the same androgen receptor even more strongly than testosterone, so that its androgenic potency is about 5 times that of testosterone. Once bound, the ligand-receptor complex undergoes a structural change that allows it to move into the cell nucleus and bind directly to specific nucleotide sequences of the chromosomal DNA. The areas of binding are called hormone response elements (HREs), and influence transcriptional activity of certain genes, producing the androgen effects. Testosterone is metabolized to 17-keto steroids through two different pathways. The major active metabolites are estradiol and dihydrotestosterone (DHT). Route of Elimination: About 90% of a dose of testosterone given intramuscularly is excreted in the urine as glucuronic and sulfuric acid conjugates of testosterone and its metabolites; about 6% of a dose is excreted in the feces, mostly in the unconjugated form. Half Life: 10-100 minutes No indication of carcinogenicity to humans (not listed by IARC). To be used as hormone replacement or substitution of diminished or absent endogenous testosterone. Use in males: For management of congenital or acquired hypogonadism, hypogonadism associated with HIV infection, and male climacteric (andopause). Use in females: For palliative treatment of androgen-responsive, advanced, inoperable, metastatis (skeletal) carcinoma of the breast in women who are 1-5 years postmenopausal; testosterone esters may be used in combination with estrogens in the management of moderate to severe vasomotor symptoms associated with menopause in women who do not respond to adequately to estrogen therapy alone. In women, excess testosterone may cause decreased breast size, a deep voice, increased genital size, irregular periods, oily skin, and unnatural hair growth. In men, excess testosterone may cause aggression, breast tenderness or enlargement, decreased testes size, and urinary urgency. Chronically high levels of testosterone are associated with at least 2 inborn errors of metabolism including: Adrenal Hyperplasia Type 3 and Aromatase deficiency. In women, testosterone may cause decreased breast size, a deep voice, increased genital size, irregular periods, oily skin, and unnatural hair growth. In men, excess testosterone may cause aggression, premature baldness, breast tenderness or enlargement, decreased testes size, and urinary urgency. 2014-08-29T06:14:17Z 2014-12-24T20:26:45Z Testosterone C00535 17347 DB00624 TES true [H][C@]1(O)CC[C@@]2([H])[C@]3([H])CCC4=CC(=O)CC[C@]4(C)[C@@]3([H])CC[C@]12C C19H28O2 InChI=1S/C19H28O2/c1-18-9-7-13(20)11-12(18)3-4-14-15-5-6-17(21)19(15,2)10-8-16(14)18/h11,14-17,21H,3-10H2,1-2H3/t14-,15-,16-,17-,18-,19-/m0/s1 InChIKey=MUMGGOZAMZWBJJ-DYKIIFRCSA-N 288.4244 288.20893014 Endogenous Solid 3.32 HMDB00234 CHEMBL386630 5791 <p>Merle G. Wovcha, Frederick J. Antosz, John M. Beaton, Alfred B. Garcia, Leo A. Kominek, &#8220;Process for preparing 9.alpha.-OH testosterone.&#8221; U.S. Patent US4221868, issued November, 1977.</p>