Androgens
May 02, 2005
By: Dr. Ewald Pretner, M.D.

Androstenedione
Androstenedione is secreted by the testes, the ovaries, and the adrenal cortex. Although of weaker biological potency than testosterone, it plays an important role in tissue growth and repair. Androstenedione has become increasingly popular among athletes for its beneficial effects on tissue resilience and its role in the conversion of adipose tissue to muscle.

As the precursor of testosterone, androstenedione helps boost and maintain testosterone levels. This is of significance in men approaching middle age, whose natural androgen production has gradually decreased as a function of the aging process, resulting in low energy and fatigue, loss of muscle mass and bone density, depressed mood and reduced sex drive.

Testosterone
Testosterone is synthesized in greatest quantities in the testes, but also in the ovaries and the adrenal cortex. In addition, it may be produced in the non-glandular tissues from precursors such as androstenedione. Less than 4% of circulating testosterone remains unbound to serum proteins and is therefore bioavailable. Testosterone is secreted in bursts of approximately 1 pulse per hour. It exhibits a diurnal variation in adult men, with the highest concentration in the early morning, followed by a decrease throughout the day.

In women, up to 50% of testosterone production arises from peripheral conversion of androstenedione to testosterone, whereas 25% is secreted by the ovaries and 25% by the adrenal glands. Excess testosterone has undesirable side effects, such as acne, hirsutism, baldness and deepening of the voice. Measuring testosterone levels in saliva represents a valuable tool for the assessment of these complaints.

In men, testosterone accounts for the male secondary sex characteristics, such as greater musculature, lower voice, and male hair growth patterns on face and body. As men age, the steady decline of testosterone levels might contribute to the above-mentioned symptoms such as fatigue, loss of muscle mass, depressed mood and low sex drive.

In both genders, testosterone is essential for the proper development of bones and muscles, and plays an important role in libido and general health.

Dihydrotestosterone
Dihydrotestosterone is the biologically most active male hormone with the same actions as testosterone. Its pattern usually correlates with that of testosterone, its precursor. As the principal androgenic hormone in a variety of tissues, DHT is responsible for the development of the male genital system during fetal life and puberty.

While DHT is of therapeutic use for its anabolic effects, too much DHT has been associated with male pattern baldness and prostate enlargement. However, since androgens decline steadily with age, the view that relative estrogen dominance, rather than a direct DHT effect might lead to prostate disease, is gaining increasing support.

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