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
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
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.
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.
mentioned above, testosterone is typically associated with men. But
testosterone is essential in women as well. In women, testosterone
- 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
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
- Free Testosterone
- Men – target = 160-400
- Women – target = 10-30
- SHBG – target < 50 nmol/ml
- Estradiol – target < 40 pg/ml
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.
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
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
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.