In the past 10 years hirsutism has been the object of a considerable
number of fundamental studies. It provides endocrinologists with an
experimental model for the investigation of androgen secretion,
metabolism and mechanism of action. Plasma androgen assay, free
testosterone measurement, hepatic and extrahepatic androgen metabolic
clearance and androgen metabolism in the skin are the different steps
which were studied by many groups and represent valuable parameters of
the mechanisms of hirsutism. Determination of the origin of androgen
oversecretion has become easier by technical progress in differential
effiuent venous catheterism, which makes it possible to compare
androgens in adrenal or ovarian effiuent veins to their peripheral
levels, and to determine the ovarian or adrenal source of the androgen
oversecretion as well as the side responsible, essential in the case of
tumors. The study of androgen metabolism and the discovery of androgen
receptors in the skin confIrm the latter as an actual target cell for
androgens. This target cell uses the circulating active androgen, i. e.,
testosterone and can also metabolize local inactive androgens into
active ones. This is the case of androstenedione and dehy-
droepiandrosterone which are the two main androgens secreted in women,
since women secrete very little testosterone. The capacity of the skin
to transform inactive androgens into active ones varies from one
individual to another. That would support the concept of variable skin
receptivity from one woman to another and from one ethnic group to
another.