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Testosterone |
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| Testosterone is the male hormone that is essential for sperm production and the development of male characteristics, including muscle mass and strength, fat distribution, bone mass and sex drive. It is the principal male sex hormone and the "original" anabolic steroid. Testosterone is secreted by the testes but is also synthesized in small quantities in the ovaries, cortices of the adrenal glands, and placenta, usually from cholesterol. In the testes, testosterone is produced by the Leydig cells. Due to the dual function of the male gonad, testosterone directly influences spermatogenesis.
As testosterone is lipid based it is able to pass through the cell membrane because the cell membrane is also partly made up of lipids. Like most hormones, testosterone is supplied to target tissues in the blood where much of it is transported bound to a
specific plasma protein, sex hormone binding globulin (SHBG). In males, the testes produce the majority of the circulating testosterone. The release of testosterone is controlled by a hormone called luteinizing hormone, or LH, which is produced by the pituitary gland (see an illustration of the pituitary gland). When the testosterone level is low, the pituitary gland releases LH, which increases the amount of testosterone produced by the testicles. The pituitary hormone LH stimulates the testicular Leydig cells to produce testosterone. In females, the ovaries produce the majority of the testosterone. The adrenal cortex produces another androgen, called DHEAS. Testosterone produced by the testes can be used by some cells as is, but other cells need testosterone in a further converted form, dihydrotestosterone (DHT). DHT influences the prostate, scalp, and beard growth. In addition, with testosterone, it plays a role in the development of the male genital tract and secondary sex characteristics.
Production of testosterone by the testes is regulated by the pituitary gland and the hypothalamus as part of a system that detects the level of testosterone in the body and regulates production accordingly. At puberty, and throughout most of the reproductive years, approximately 10-20 times more testosterone is synthesized in males than in females. For males at puberty, testosterone and DHT play an important role in the development of secondary male sexual characteristics, and for women oestrogen again plays the most important role. In adult males, testosterone levels are critical in the evaluation of impotence and infertility. Testosterone is the principal androgen in men and is required for normal sperm production. In both sexes, testosterone enhances aerobic metabolism and increases protein synthesis. |
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Functions and health benefits of testosterone |
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Testosterone is a male sex hormone required for sperm production, the development of male reproductive organs and the emergence of secondary male sexual characteristics such as facial hair, a deeper voice and muscles. Testosterone has two different effects on the body: anabolic effects which promote growth and muscle building, and androgenic effects which develop the male sex organs and secondary sex characteristics such as deepening of the voice and growth of facial hair. Testosterone is centrally involved in spermatogenesis and the development of secondary male sexual characteristics. Testosterone and other related hormones in the body (also known as androgens) clearly play important physiological roles in women.
Testosterone is necessary in the fetus for the development of male external genitalia. Increased levels of testosterone at puberty are responsible for further growth of male genitalia and for the development and maintenance of male secondary sex characteristics such as facial hair and voice changes. Testosterone stimulates the development of the penis and testes, growth of facial and pubic hair, deepening of the voice, changes in body-shape, and increased muscle mass. It helps maintain sex drive and the production of sperm cells.
Testosterone is our most important anabolic hormone, meaning that it helps cells create energy from the food we eat, builds stronger bones and muscles, and is needed by the brain for normal brain function. Maintaining sufficient levels of the hormone can lower LDL cholesterol, triglycerides and fibrinogen, raise HDL cholesterol and human growth hormone (HGH), lower blood pressure, normalize abnormal heart rhythms and angina, improve insulin resistance, build muscle and decrease body fat. Testosterone is also associated with protein synthesis stimulation and amplified muscle development. Mood is also affected by testosterone, and low levels of the hormone can cause depression as well as fatigue. |
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Low testosterone symptoms |
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When there is not enough testosterone circulating in the body, it can cause a wide range of signs and symptoms. Symptoms related to low testosterone include decreased sex drive, increased risk of osteoporosis, body hair loss, reduced muscle mass and strength, weaker erections and orgasms, lowered sperm count, hot flashes, fatigue, trouble concentrating and depression. Men who have a severe and prolonged reduction of testosterone also may experience loss of body hair, reduced muscle mass and decreased bone mass. Testosterone deficiency is associated with a higher risk of heart disease and depression. |
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Testosterone replacement therapy |
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Treatment for testosterone deficiency is based on testosterone replacement therapy. Testosterone replacement therapy is an option for men whose natural testosterone level is not within the normal range. Testosterone replacement has been used to treat some postmenopausal symptoms, especially lack of libido in women who have received chemotherapy. It has also been used effectively in the treatment of anemia and the weakness and muscle wasting syndrome associated with AIDS. Several FDA-approved therapies are available, with different delivery methods to suit individual preference. Testosterone can be administered by tablet, patch, injection or implant. Testosterone replacement gels are the newest type of delivery method. The gel is applied once daily to the upper arms, shoulders and/or abdomen. Testosterone replacement patches are worn for 24 hours and changed daily. The patch is applied to the upper arms, thighs or torso. Testosterone injections are given either every week or every two to three weeks. With testosterone injections, the symptoms of low testosterone may fluctuate because it creates abnormal highs and lows in hormone levels.
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Side effects of testosterone replacement therapy |
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| The side effects of testosterone replacement therapy are not common once levels are restored to the normal range. Many of the unwanted side effects of testosterone and anabolic steroids come from their androgenic properties. Such side effects include masculinisation with acne and excess body hair, scalp hair loss, fluid retention, deepening of the voice, enlargement of the clitoris and adverse effects on blood cholesterol. Testosterone replacement therapy may worsen prostate disease. Testosterone can make prostate cancers grow, so testosterone replacement therapy could cause an unnoticed prostate cancer to produce symptoms or become lethal. Testosterone also worsens benign prostatic hyperplasia, a noncancerous enlargement of the prostate. Excess testosterone can cause acne, headaches, anxiety, irritability and even rage. Because excess testosterone spills over and becomes estrogen, it can cause water retention, breast enlargement, prostate enlargement, atrophy of the genitals, decrease in libido, and cancer. |
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