Testosterone is a steroid hormone from the androgen group. Although most people associate testosterone with men (and with body builders!), women make it also, though in much smaller amounts. Testosterone is secreted in the testes of men and the ovaries of women. It is the principal male sex hormone and the “original” anabolic steroid. In both males and females, it plays key roles in health and well-being. Examples include enhanced libido (sex drive), energy, immune function, and protection against osteoporosis.
In our practice, we check testosterone levels in patients complaining of persistent fatigue, symptoms of Fibromyalgia, chronic muscle aches or sense of muscular weakness, or who demonstrate evidence of poor or slow healing.
Sources of testosterone
Like other steroid hormones, testosterone is derived from cholesterol. The largest amounts of testosterone are produced by the testes in men, but it is also synthesized in smaller quantities in women by the ovaries, by the placenta, as well as by the adrenal gland in both sexes. Like most hormones, testosterone is supplied to target tissues by the blood where much of it is transported bound to a specific plasma protein, sex hormone binding globulin (SHBG).
Effects of testosterone
In general, androgens promote protein synthesis and growth of tissues that have androgen receptors. Testosterone effects can be classified as virilizing and anabolic effects, although the distinction is somewhat artificial, as many of the effects can be considered both. Anabolic effects include growth of muscle mass and strength, increased bone density and strength, and stimulation of height growth and bone maturation. Therefore, testosterone is important as part of the body’s normal maintenance and repair processes. Virilizing effects include maturation of the sex organs, particularly the penis and the formation of the scrotum in fetuses, a deepening of the voice in both sexes at puberty, and growth of facial and body hair. Testosterone derivatives are also often used (illegally) by bodybuilders to enhance muscle building, and by athletes to enhance performance.
In addition, in the brain and bones, testosterone gets metabolized (converted) to estradiol (a form of estrogen). In the bones, estradiol accelerates maturation of cartilage into bone, leading to closure of the growth plates and conclusion of normal growth. In the central nervous system, estradiol, rather than testosterone, serves as the most important feedback signal to the hypothalamus, a portion of the brain that links the nervous system to the endocrine system, which helps control the release of many hormones in the body.
As mentioned above, testosterone is typically associated with men. But testosterone is essential in women as well. In women, testosterone contributes to:
- Improved sense of well-being
- Increased strength, especially in the upper body
- Increased repair mechanisms (protein synthesis)
- Increased libido
- Increased nipple and clitoral sensitivity
- Increased bone mineral density
Low testosterone levels are associated with:
- Loss of lean muscle mass
- Increased fat
- Increased risk of cardiovascular disease
- Loss of libido (sex drive and interest)
- Hopelessness, helplessness, depression
- Erectile dysfunciton
- Decreased enthusiasm
- Muscle & joint pain
- Impaired healing
Measuring Testosterone Levels
Testosterone can be measured in both the blood and saliva. While most labs have established “normal” ranges, optimum testosterone blood levels are listed below. In addition, PSA (prostate-specific antigen) levels should be measured in men, and sex hormone binding globulin (SHBG) and estradiol levels should also be measured (estrogen blocks the receptor sites for testosterone, especially in men).
- PSA should be <4.0
- Total Testosterone
- Men – target = 750-110
- Women – target = 40-85
- Men – target = 160-400
- Women – target = 10-30
Although testosterone supplementation is available in commercially-prepared forms, bio-identical hormone replacement—replacing exactly what your body makes—is preferred. We give patients a prescription for a custom-formulated cream that is prepared by a compounding pharmacy. (Your local CVS or Walgreen’s does not have compounding capabilities. They only dispense medications.) The cream is applied to the skin where it gets absorbed directly into the blood stream.
For men, testosterone supplementation usually starts at 50-200 mg a day, depending on initial test results. For women, we usually start at 1-5 mg a day. Dosing is adjusted based on subsequent lab testing and patient symptoms. The advantages of using a custom compounded cream include the ability to fine-tune the dose and the ability to mix other hormones in the cream.
Some patients (about 15%) do not absorb medications well through the skin. In those cases injectable testosterone, as Depotestosterone cypionate, is available. It most commonly comes in vials containing 200 mg (1 cc) of the drug. Injections are best given twice weekly.
Labs should be rechecked in a month after starting therapy or after changing doses.
Potential Side Effects of Testosterone Replacement Therapy
When used under careful medical supervision, testosterone replacement is safe and effective, especially if it used to replace low or suboptimal levels. However, it important to keep an eye open for potential side effects. If side effects do occur, they are almost always mild and reversible.
Testosterone can exert a negative feedback on the Hypothalamic-Pituitary-Testicular axis. This can affect other hormone levels. Women can experience acne or the eruption of facial hair. Men can experience testicular atrophy (shrinking testicles). Male pattern baldness can occur. Since testosterone can get metabolized to estrogen, there is theoretically an increased risk of benign prostatic hypertrophy (BPH) or prostate cancer. In addition, reflective of potential increased estrogen, there is a risk of increased fat deposition around the trunk, and the development of enlarged breast tissue in men.