DHEADehydroepiandrosterone

DHEA is produced by the adrenal glands and is the most abundant circulating steroid hormone in humans. It is largely a precursor: tissues convert it into androgens and oestrogens as needed. Levels peak in the twenties and decline steadily thereafter.

It matters because that age-related decline made it an early candidate for anti-ageing supplementation. Decades of trials have found little to support the claims — small and inconsistent effects on body composition, mood and wellbeing in healthy adults, with clearer benefit only in people with genuine adrenal insufficiency.

In practice it is sold freely as a supplement in the United States but is a prescription-only medicine in the UK and much of Europe. It is on the WADA prohibited list, and it can raise oestrogen and androgen levels with the side effects that implies.