Vulvar acanthosis nigricans: a marker for insulin resistance in hirsute women

To determine the frequency of acanthosis nigricans (AN) in a group of hirsute, hyperandrogenic women and to determine the body site most frequently affected. Cross-sectional observational study. University teaching hospital. Reproductive age, nonhypertensive, nondiabetic women referred for evaluation of hirsutism, documented to have hyperandrogenism, without medications known to influence lipid, carbohydrate, or hormonal metabolism. None Presence of AN. Insulin resistance was assessed by measuring fasting glucose, fasting insulin, and nadir glucose after a 0.1U/kg IV insulin bolus in both obese and nonobese, hirsute, hyperandrogenic women. Twenty-four of 43 women were found to have AN. Although AN was identified at several body sites including the axilla (n=14), on the nape of the neck (n=13), below the breasts (n=7), and on the inner thigh (n=7), it was always present on the vulva in women who displayed one or more lesions. Acanthosis nigricans was found only in the obese, hirsute, hyperandrogenic women. These women were the most insulin resistant. Acanthosis nigricans and insulin resistance are found frequently in obese, hirsute, hyperandrogenic women. The vulva is the most likely place to find this marker.