Andropause

The andropause syndrome is difficult to detect clinically because the symptoms are often attributed to a more general aging process in the absence of specific disease. The characteristic symptoms include weakness, depression, fatigue, and changes in body hair and skin. In addition there is loss of libido, lean body mass, and bone mass, as well as decreased intellectual activity and spatial orientation ability. The severity and frequency of each symptom are variable.

Erectile function. Male aging is associated with a decline in sexual interest and activity and an increase in erectile dysfunction. In men between the ages of forty and seventy, 52 percent reported some degree of impotence (Gooren). This aging-related impaired sexual function is multifactorial with testosterone likely playing only a minor, if any, role. Testosterone appears more important in maintaining desire and nocturnal erections (Gooren). For most men with erectile dysfunction, therapies such as sildenafil (Viagra©), penile injections, vacuum-suction devices, and penile prostheses are more effective than testosterone.

Mood and cognition. Testosterone replacement often improves men's sense of overall well-being (Vermeulen). Improvements in libido, energy, and mood; a decline in anxiety; and increased aggressiveness in business transactions have all been described in hypogonadal (having low levels of testosterone) men receiving testosterone (Tenover 1992, 1994; Wang et al.), but how these findings translate to normal aging men is not clear.

Body composition. A decrease in both muscle tissue mass and some aspects of muscle strength have been associated with male aging (Tenover 1994). An increase in percent body fat has been reported in hypogonadal men compared to eugonadal men (Katznelson et al.). A role for testosterone in these changes is supported by the fact that testosterone replacement in young, healthy, hypogonadal men increases fat-free mass, muscle size, and strength, and decreases percent body fat (Bhasin et al.; Katznelson et al.; Tenover 1992). Several studies have reported an increase in grip strength with testosterone replacement (Morley et al.; Sih et al.), but the effect on more clinically relevant measures of strength is not known.

Bone density. Osteoporosis is a significant but underrecognized cause of morbidity and mortality in elderly men. As in women, bone density decreases and osteoporotic fractures increase with male aging (Abu et al.; Swerdloff and Wang). Hypogonadism is associated with a significant decrease in bone density (Katznelson et al.) and increased risk of fractures. Testosterone replacement significantly improves bone mineral density in hypogonadal men (Behre et al.; Katznelson et al.), but a reduction in fractures following normalization of bone mineral density has not been established.

Androgen levels. Only 1-2 percent of the testosterone in the circulation is free; the remainder is bound, either tightly to sex-hormonebinding-globulin (SHBG; 60 percent), or weakly to albumin (40 percent). Bioavailable testosterone includes only the free and albumin bound components. SHBG-bound testosterone is not available for tissue uptake (Gray et al.).

Bioavailable testosterone declines, and SHBG-bound testosterone increases, with increasing age. The implication of this is that hypogonadal men may have normal or only slightly reduced total serum testosterone levels. For this reason identification of these men is best accomplished by measurement of bioavailable testosterone (Gray et al.).

The clinical significance of the age-related decline in testosterone is unclear. There is considerable variation in serum testosterone among men of all ages, such that many healthy elderly men have levels within the normal range (Vermeulen). Total testosterone levels below the normal reference level are reported in 7 percent of men age forty to sixty, 20 percent of men age sixty to eighty, and 35 percent of men over eighty (Vermeulen and Kaufman).