Hidradenitis suppurativa: an androgen-dependent disorder.

The demonstration by Mortimer et al. (1986a; this issue, p. 263) that hidradenitis suppurativa responded to treatment with the antiandrogen cyproterone acetate, in a meticulously assessed double-blind trial, substantiates the view that the condition is androgen-dependent. Such a hypothesis was first advanced in the anecdotal report (Ebling et al, 1979) referred to by Mortimer et al, and details of the original four cases are now also published (Sawers, Randall & Ebling, 1986). Hidradenitis suppurativa is a disorder of the pubic and axillary regions where, in both sexes, the skin is characterized by the presence of terminal hair and functional tubular (so-called apocrine) glands. The pubic and axillary hair is dependent on low levels of androgen for its development. Since apocrine units, often in association with holocrine lipid secreting glands, form hormonally controlled scent organs in many mammals (Ebling, 1977), there are phylogenetic grounds for postulating similar endocrine control—and, indeed, similar odorous function—in man. It is likely that sebaceous as well as apocrine glands are involved in hidradenitis; indeed, Plewig has argued for the inclusion of the hair follicle to form a triad of affected organs (see discussion in Ebling et al, 1979). Two important questions need to be discussed. The first is whether the disorder results from an abnormally high level of free androgen or whether an enhanced response of the target organs is the critical factor. The second is the extent to which the success of the hormonal therapy can be ascribed to the undoubted lowering of free androgen which it achieves, to blockage of the androgen receptors, or to modification of peripheral testosterone metabolism. Such questions are, of course, of equal moment in considering the causation and treatment of other androgendependent disorders. That hirsutism, alopecia and acne in women can result from over-production of androgen in cases of overt endocrine disturbance is not in doubt. The issue is whether such conditions can be ascribed to abnormally high systemic androgen levels in the absence of obvious disease. Modern techniques for the assay of hormones in body fluids have now made it moderately easy to show that in some patients the level of free testosterone in the plasma is high, within or a little above the normal range. From published data on hirsutism, alopecia and acne, it is usually possible to deduce that the mean total testosterone is significantly higher, or the mean sex hormone binding globulin (SHBG) lower, in patients than in control subjects. If the differences appear undramatic, the calculation of the testosterone/SHBG quotient may sometimes produce a more convincing result. Such demonstrations, carefully analysed and presented, give joy to the investigators. The pattern has, for example been nicely elucidated for acne by Darley et al