Testosterone is commonly referred to as the male sex hormone, but it affects the male in ways other than libido. The male testes and, to a lesser extent, the adrenal glands and ovaries produce testosterone. In females, half of the testosterone is produced by the ovaries and the adrenal gland, and the rest is produced by converting other androgens.
The production of testosterone begins with puberty and declines by about 1% each year after age 30.
Testosterone either binds to androgen receptors or is converted to 5α-dihydrotestosterone (D.H.T.) by the enzyme 5α-reductase, which then binds to androgen receptors. D.H.T. is a more potent androgen than testosterone. Once testosterone or D.H.T. is bound to the androgen receptor, the hormone and receptor enter the cell’s nucleus and bind to special D.N.A. sequences known as hormone response elements. As a result, proteins are produced. These proteins have androgenic effects all over the body.
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Testosterone is a hormone or chemical messenger. It is classified as an androgen. Androgens are essential for the development of male reproductive organs, secondary sexual characteristics, libido, and sperm production. In men, a small amount of testosterone is converted to estradiol, a form of estrogen.
In men, testosterone has both anabolic and androgenic effects. Its anabolic effects promote an increase in muscle and bone strength and muscle mass. Its androgenic effects promote the primary and secondary sex characteristics.
In men, testosterone helps maintain and support:
In women, testosterone helps maintain and support:
Testosterone levels are tightly regulated in both men and women. Any disorder that causes a decrease in testosterone production is referred to as hypogonadism. Both medical conditions and lifestyle choices can have an impact on testosterone levels.
Lifestyle factors that can affect testosterone levels:
Medical conditions that can affect testosterone levels:
Causes of low testosterone levels in women:
Having a high level of naturally occurring testosterone is unusual. Potential causes of high testosterone levels include tumors, using anabolic steroids, and taking testosterone supplements.
However, when testosterone levels are too high, potential side-effects include:
High testosterone levels in women are more common. Syndromes that cause increased testosterone levels in women include polycystic ovary syndrome and congenital adrenal hyperplasia.
Hypogonadism, or low testosterone levels in men, results from a problem producing testosterone in either the testes or the pituitary gland/hypothalamus.
Symptoms of low testosterone in men may include:
The primary symptoms of low testosterone levels in women are loss of sexual desire and fertility problems. Low testosterone levels may also adversely impact cardiovascular health, cognitive function, muscle strength and mass, and bone density. However, further research is needed before testosterone supplementation can be recommended in postmenopausal women except for the treatment of low sexual desire associated with hypoactive sexual desire disorder.
The F.D.A. and the American Urological Association have both endorsed the use of testosterone supplementation for medical and genetic conditions that result in symptomatic low testosterone levels.
The first step in diagnosing any medical condition is to obtain a complete medical history and undergo a physical exam.
Your health care provider may order the following laboratory tests:
Total testosterone level: In most cases, two separate testosterone levels are obtained, with both levels taken before noon, as testosterone levels tend to naturally decrease later in the day. Normal testosterone levels for adult males range between 280 and 1,100 nanograms per deciliter (ng/dL) and between 15 and 70 ng/dL for adult females. Normal lab values can differ between labs.
Luteinizing hormone (L.H.): L.H. stimulates testosterone production in the testes. Abnormal levels may indicate a pituitary gland problem.
Blood prolactin level: Prolactin is a hormone that stimulates breast development and milk production in the female. Increased levels in men may be a sign of a benign pituitary tumor, among other things.
Blood hemoglobin/hematocrit level: Low hemoglobin levels may indicate a medical problem, such as anemia. Red blood cell production may increase because of testosterone replacement therapy. As a result, a baseline hemoglobin/hematocrit level is recommended both before and after treatment.
Additional lab tests or studies may be required based on your blood test results and your medical history.
The American Urological Society defines low testosterone (Low-T) as less than 300 nanograms per deciliter (ng/dl). Testosterone levels may fluctuate throughout the day. However, they are typically highest in the morning and lowest at night.
Following the completion of your history forms and the evaluation of your blood panel results, a licensed Invigor Medical health care provider in your state will review your lab results and discuss treatment options with you.
If the Invigor Medical health care provider determines that you are a good candidate for testosterone replacement therapy, they will send a prescription to either our compounding pharmacy partner or your local pharmacy for intramuscular testosterone injections and supplies.
While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.