| Item |
Information |
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Drug Groups
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approved; investigational |
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Description
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Testosterone is a steroid sex hormone found in both men and women. 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. |
| Indication |
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. |
| Pharmacology |
Testosterone is a steroid hormone from the androgen group. Testosterone is primarily secreted from the testes of males. In females, it is produced in the ovaries, adrenal glands and by conversion of adrostenedione in the periphery. It is the principal male sex hormone and an anabolic steroid. In both males and females, it plays key roles in health and well-being. Examples include enhanced libido, energy, immune function, and protection against osteoporosis. On average, the adult male body produces about twenty times the amount of testosterone than an adult female's body does. |
| Toxicity |
Side effects include amnesia, anxiety, discolored hair, dizziness, dry skin, hirsutism, hostility, impaired urination, paresthesia, penis disorder, peripheral edema, sweating, and vasodilation. |
| Affected Organisms |
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Humans and other mammals |
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| Biotransformation |
Testosterone is metabolized to 17-keto steroids through two different pathways. The major active metabolites are estradiol and dihydrotestosterone (DHT). |
| Absorption |
Approximately 10% of the testosterone dose applied on the skin surface is absorbed into systemic circulation |
| Half Life |
10-100 minutes |
| Protein Binding |
40% of testosterone in plasma is bound to sex hormone-binding globulin and 2% remains unbound and the rest is bound to albumin and other proteins. |
| 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. |
| References |
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Freeman ER, Bloom DA, McGuire EJ: A brief history of testosterone. J Urol. 2001 Feb;165(2):371-3.
[Pubmed]
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Hoberman JM, Yesalis CE: The history of synthetic testosterone. Sci Am. 1995 Feb;272(2):76-81.
[Pubmed]
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Contraceptive efficacy of testosterone-induced azoospermia in normal men. World Health Organization Task Force on methods for the regulation of male fertility. Lancet. 1990 Oct 20;336(8721):955-9.
[Pubmed]
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| External Links |
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