The first signs of declining testosterone are generally vague. Symptoms-what you experience, your medical complaints-may not be investigated at a traditional medical office or could be attributed to psychosocial stress factors or "aging."

Decline in muscle mass or strength. Diminished testosterone directly correlates with a decrease in the synthesis rate of muscle proteins, contractile structure formation and the force-generating capabilities of muscle cells. Muscle mass declines increase risks for falls and fractures.

Body fat mass increased. Abdominal fat, pectoral fat and increased leptin levels (peptide hormone produced by fat cells) are all correlated to low testosterone levels.

Decreased bone mass. Up to 30% of men (60 years and older) may become osteoporotic-and one in six of them will fracture a hip at some point in his life.

Sex drive/sexual thoughts declined. Both of these decrease prior to actual declines in sexual performance.

Increased erectile dysfunction (ED). Testosterone is produced in the testicles. When low, ED may be a potential byproduct.

Coronary artery disease, cholesterol derangement. Population studies link low testosterone levels and higher risk for atherosclerotic cardia disease and also atherosclerotic obstruction when coronary artery disease is present.

Lowered energy levels and sense of well-being. These and non-specific irritability frequently are the first signs of declining testosterone levels, but the most overlooked.

Stamina and exertional performance decline. A decrease in testosterone can be graphed to correlate with functional declines in professional athletes and other "performance-minded" people.

Reduced cognitive skills, concentration, memory. Lowered testosterone levels are strongly linked to cognitive decline (even Alzheimer's) and diminished visuospacial memory.