Dehydroepiandrosterone (DHEA) is a steroid hormone naturally present in the plasma of humans. It is also present in a sulphated form DHEA-sulphate (formed by steroid sulphatases), which represents around 99 % of the total DHEA concentration in plasma. In humans, DHEA is secreted by the adrenal glands with peak levels occurring at around age 25 years. From about age 30 years, DHEA levels begin to decline such that by age 75 years, the plasma levels of DHEA will have declined by 80 % from their peak level. This is important because DHEA can act as a substrate for the formation of testosterone, although it can also be converted to androstenedione and dihydrotestosterone, or aromatised to oestrogen. As testosterone levels also decline with age, it has been suggested that DHEA supplementation may increase testosterone levels in those who have experienced a decline due to ageing. A number of studies have investigated the effects of DHEA-sulphate supplements of elderly individuals.
For example, in one study, researchers1 investigated the effects of 50 mg of DHEA for 10 months in elderly men and women aged 65 to 78 years. Subjects had their DHEA levels measured at baseline and these were on average around 80 % of those that would be expected at age 25 years, suggesting a large age-related decline in DHEA levels in the subjects. Subjects were divided into either a DHEA plus exercise group or a placebo plus exercise group, performing exercise in the last 4 months of the 10 month study. The researchers assessed the body composition and strength of the subjects prior to the resistance training phase, but during this time, the DHEA was no effective at improving either strength or thigh muscle size. However, in combination with resistance training the DHEA was effective at significantly improving the muscle strength and thigh muscle volume compared to the placebo. The DHEA supplements therefore augmented the effects of strength training in the subjects.
The researchers then investigated whether the testosterone levels of the subjects had increased, as this may explain the increases in strength and thigh volume. Measurements of testosterone in the subjects showed that while the women had experienced increases in testosterone, the men had not. The DHEA supplements in this study actually caused a 3-fold increase in testosterone levels in the women, which may explain the muscle building properties of DHEA in women, although even with a 3-fold increase the levels of testosterone were still relatively low at the end of the study. However, DHEA may increase the effects of resistance training through mechanisms other than increasing testosterone levels in the case of men. One mechanism that has been suggested is that DHEA may increase insulin-like growth factor 1 (IGF-1) in skeletal muscle, and this may create an anabolic effect. Supplements of DHEA may also inhibit the catabolic activity of glucocorticoids and thus may provide an anabolic effect in this way.
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