Testosterone, produced mainly in the testes and adrenal glands facilitates the development of male sex characteristics such as facial hair, muscle mass, and deep voice. It is also responsible for a strong libido and the production of sperm.
Free “T”
Much of the testosterone produced by the body attaches to proteins, albumin and sex hormone binding globulin (SHBG). Free testosterone refers to the free circulating hormone that remains “unattached”. Both albumin-bound testosterone and free testosterone are considered bioavailable, or immediately ready for use by the body.
Too Much Testosterone
While a mild-to-moderate increase in testosterone levels may not cause symptoms in most males, a number of symptoms and medical conditions are associated with “high” testosterone levels. These are dependent on age, other health conditions, current medical treatments, and use of testosterone for enhanced physical ability and athletic prowess.
Males with elevated testosterone may be at increased risk for the following:
Prostate cancer
Worsening of Benign Prostate Hypertrophy (BPH)
Liver toxicity
Increased sleep apnea
Congestive heart failure
Gynecomastia (male breasts)
Infertility
Causes of Elevated Testosterone
The most common causes of higher than normal testosterone levels in males include:
Genetic conditions including adrenal hyperplasia
Adrenal tumors
Testicular tumors
Testosterone/gonadotropin abuse
Testosterone replacement therapy (TRT)
Testosterone replacement therapy (TRT) may be recommended for men diagnosed with symptomatic hypogonadism. This condition is generally characterized by fatigue, erectile dysfunction, altered body composition, cognitive disruption and metabolic changes. Treatment has been succesful for many men, restoring libido and sexual function, raising energy levels, increasing bone density and adding protection from cardiovascular disease.
Side effects from testosterone replacement therapy include:
Polycythemia (excess red blood cells)
Peripheral edema
Cardiac dysfunction
Hepatic dysfunction (liver condition)
Change in hair patterns
Decreased spermatogenesis
Acne due to increased sebum secretion
Testosterone replacement therapy, designed to restore the body to natural levels of testosterone function, has been linked to prostate cancer, BPH, and OSA (obstructive sleep apnea). Exogenous testosterone creates an imbalance in the hypothalamic-pituitary axis. Because of this, testosterone converts to estrogen causing many symptoms including gynecomastia (male breasts) and/or pain in the breast area. In adolescents TRT is associated with higher than normal levels of aggression and an increased rate of suicide.
Some topical and injectable (intramuscular) testosterone has been known to cause skin irritation including, erythema (specific rash) and pruritus (itching condition) in 60% of patients.
Testosterone, Free
The following table indicates normal a.m. levels of free testosterone for males by age.
<1 year: Term infants 1 to 15 days: 0.20-3.10 ng/dL* 16 days to 1 year: Values gradually decrease from newborn (0.20-3.10 ng/dL) to prepubertal levels. 1-8 years: <0.04-0.11 ng/dL 9 years: <0.04-0.45 ng/dL 10 years: <0.04-1.26 ng/dL 11 years: <0.04-5.52 ng/dL 12 years: <0.04-9.28 ng/dL 13 years: <0.04-12.6 ng/dL 14 years: 0.48-15.3 ng/dL 15 years: 1.62-17.7 ng/dL 16 years: 2.93-19.5 ng/dL 17 years: 4.28-20.9 ng/dL 18 years: 5.40-21.8 ng/dL 19 years: 5.36-21.2 ng/dL Males (adult): 20 – <25 years: 5.25-20.7 ng/dL 25 – <30 years: 5.05-19.8 ng/dL 30 – <35 years: 4.85-19.0 ng/dL 35 – <40 years: 4.65-18.1 ng/dL 40 – <45 years: 4.46-17.1 ng/dL 45 – <50 years: 4.26-16.4 ng/dL 50 – <55 years: 4.06-15.6 ng/dL 55 – <60 years: 3.87-14.7 ng/dL 60 – <65 years: 3.67-13.9 ng/dL 65 – <70 years: 3.47-13.0 ng/dL 70 – <75 years: 3.28-12.2 ng/dL 75 – <80 years: 3.08-11.3 ng/dL 80 – <85 years: 2.88-10.5 ng/dL 85 – <90 years: 2.69-9.61 ng/dL 90 – <95 years: 2.49-8.76 ng/dL 95-100+ years: 2.29-7.91 ng/dL
Increased Levels of Testosterone
When testosterone levels in adult men exceed the upper limit of normal ranges by over 50%, testicular or adrenal tumors may be suspected, or possible androgen abuse (steroids).
Testosterone Replacement Therapy Monitoring
The goal of treatment is to achieve testosterone levels within the normal range on average, with peaks that are not too far above the range for normal young adults.
Bioavailable and Free Testosterone: In general, bioavailable testosterone levels, when combined with free testosterone equal that of total testosterone. Some medical conditions or drugs however, may affect total testosterone concentration, bioavailable, or free testosterone levels. These include:
Sex steroids Genetic abnormalities
Liver disease
Systemic illness
Delayed puberty
Mild hypogonadism
Testing Free Testosterone
Testosterone levels fluctuate throughout the day with early morning levels 50% higher than nighttime concentrations. Several measurements may be taken to confirm a medical condition, or to help determine treatment if necessary. If free testosterone levels indicate below or beyond the normal range for your age, contact your primary care physician or an endocrinologist for further tests and possible diagnosis.