Testosterone is an anabolic (or building) hormone. The age-related decline in testosterone levels is associated with the following identifiable signs or symptoms:

• A decline in muscle mass and strength. Loss of muscle
  volume and tensile strength are hallmarks of aging. Diminishing
  testosterone levels directly correlate with a decrease in the
  synthesis rate of muscle proteins, formation of contractile
  structures and the force generating capabilities of muscle cells.
  Declines in muscle mass are also correlated with increased risk
  for falls and fractures.
• Increase in body fat mass, particularly abdominal fat and pectoral fat. Sometimes, Gynecomastia, (enlargement of breast tissue in men) may occur. Decreases in testosterone are also associated with increasing levels of leptin. Leptin is a peptide hormone produced by fat cells and its circulating levels are directly reflective of an individual's fat mass. Adequate testosterone levels and lean mass are inversely correlated with leptin levels.
• Decrease of bone mass. Studies indicate that age and associated declines in testosterone levels correlate with bone loss in men. Declines in Estradiol and testosterone levels are associated with bone loss in women as well, and this phenomenon appears at an earlier age and at a more rapid rate compared to men. Up to 30% of men aged 60 and over may become osteoporotic. One in 6 will fracture a hip at some point in his life. Women are hormonally and statistically more complex than men. Female hormone replacement studies do not separate the effects of estrogens and testosterone, but do show benefits of proper overall hormone replacement programs. An unsupplemented woman will at ages 60 - 80, show a 50% reduction in her original bone mineral density and 1 in 4 will suffer a vertebral or hip fracture.
• Decline in sex drive and frequency of sex thoughts. Interestingly, this decline precedes declines in actual performance.
• Increased frequency of erectile dysfunction in men and diminished sexual response and pleasure in women.
• Decreased sense of overall well being, perception of energy level and vigor. These types of complaints, along with non-specific irritability, are frequently the first symptoms associated with declining testosterone levels, but are the most often overlooked or attributed to stress or "not being as young as you used to be."
• Decline in stamina and exertional performance. A graph of the declines in testosterone and growth hormone levels can be placed over a graph of the percentage of professional athletes still performing at a given age, with essentially identical shapes. Other "performance-minded" individuals, like business executives and people whose careers demand multi-tasking or complex problem solving skills, also frequently note similar functional declines.
• Decline in cognitive skills, concentration and memory. Studies show declining testosterone level is strongly associated with cognitive decline and diminished visual-spatial memory.
• Coronary artery disease and cholesterol derangement. In population studies, low levels of testosterone are associated with increased risk of atherosclerotic cardiac disease. Older men treated with testosterone can show decreases in total cholesterol and LDL (bad cholesterol). Low testosterone levels are also correlated with a greater degree of atherosclerotic obstruction when coronary artery disease is present.

The goal of testosterone replacement therapy is to minimize, prevent or reverse the affects of our age related decline. The beneficial effects of attaining healthy testosterone levels are seen for both men and women and are essentially the inverse of the aforementioned list of problems. Of course, the goals for testosterone level are appropriately lower for women.

Testosterone Therapy

While the clinical indicators of testosterone decline may give a care provider a notion that an individual may be a candidate for testosterone replacement, objective measures must be obtained to properly institute and manage therapy and rule out and address accompanying medical problems.

To adequately measure testosterone levels, both total and free testosterone studies should be evaluated. For males: a level of 260-1,000 ng/dl is given as the normal laboratory range from men aged 20-70. For females, this range is 15-70 ng/dl. Free testosterone levels average approximately 2% of the total, 50-210 pg/mi for men and 1-10 pg/mi for women. Free testosterone is the slightly more valuable of the two, as it reflects the amount of testosterone available to perform useful work at any one moment.