The assumption that the metabolism of testosterone to 5α-dihydrotestosterone (5α-DHT) is required for androgen action in the skin was investigated by studying the uptake and metabolism of testosterone by skin and other tissues of the rat in vivo. The skin resembled the classical androgen target organs in the uptake and retention of radioactivity, but the proportions of the steroids present were markedly different. In the ventral prostate most of the testosterone was metabolized, mainly to 5α-DHT, after only 20 min. In the skin testosterone was always the predominant steroid identified and androstenedione, 5α-DHT, 5α-androstane-3α, 17β-diol, androsterone and 5α-androstane-3β, 17β-diol were only present in much smaller quantities, even after 5 h.

Hypophysectomy, known to reduce the response of the sebaceous glands to testosterone in the rat, did not alter the steroid composition in the classical target organs, the preputial glands, or the plasma, but in the skin it increased testosterone metabolism without altering the levels of 5α-DHT or the 5α-androstane-diols. These results suggest that the 5α-reduction of testosterone to 5α-DHT may not be so important in the skin, or at least in the sebaceous glands, as it is in the prostate.