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DHEA secretion begins during fetal life, reaches a peak in the third decade, and declines steadily thereafter; the level at age 80 is only 10-20% of the peak level. This decline has been speculatively associated with the changes of aging. Commercial formulations of DHEA are marketed as dietary supplements, although this substance is neither a nutrient nor a component of the human food chain. DHEA has been promoted for the prevention of degenerative diseases including atherosclerosis, Alzheimer dementia, parkinsonism, and other effects of aging. None of the alleged benefits has been demonstrated in large, randomized clinical trials. Limited studies in animals and human subjects suggest that DHEA reduces the percentage of body fat, perhaps by blocking the storage of energy as fat. Long-term administration to postmenopausal women has been associated with insulin resistance, hypertension, and reduction of LDL cholesterol levels. An analysis of 16 preparations of DHEA by high-performance liquid chromatography showed a variation in content from 0-150% of the labeled strength; only seven products fell between the expected 90-110% of labeled strength.