Testosterone is the predominant male hormone. Testosterone is converted to DHT which produces male sexual characteristics. If testosterone is not converted to DHT, it is converted to estradiol, the female hormone which generates the female appearance such as enlarged breast, reduced body hair.

The daily production of testosterone in young healthy men is 7mg a day. The circadian rhythm of testosterone is 20% higher in the morning than evening.

Testosterone producing leydig cells dies in the testicles every 4 seconds. Only one-third of the 700 million leydig cells remain at age 70-80 and free testosterone levels decreases by more than 50% in the blood and urine. Thus men will experience the mental and physical symptoms of testosterone deficiency.

Roles of testosterone in men

• safeguards the cardiovascular system
• maintains reproductive health, sexual potency, prostate , body hair
• supports the brain and nerve by increasing blood supply
• sustains the bones
• improves mood and memory
• Protects against obesity and diabetes, reducing fat mass and increasing lean muscle mass.

Lab test to confirm diagnosis of testosterone in men include total testosterone, androstanediol glucuronide, SHBG, estradiol, FSH, 24 hr urine testosterone, androsterone and etiocholanolone.

Aging men have elevated estrogens in the blood, especially estradiol. This is because older men have more body fat. High estrogen levels are associated with aging problems such gynaecomastia, impotence, benign prostate hypertrophy.