Acanthosis nigricans, hirsutism, insulin resistance and insulin receptor defect

A 24-year-old negress with the triad of acanthosis nigricans, hirsutism associated with polycystic ovaries and insulin resistance is reported. Metabolic studies were done 3 years after a bilateral ovarian wedge resection. Partial remission of the hirsutism and return of menstrual cycles occurred after surgery. Extreme resistance to endogenous and exogenous insulin was observed. Three studies of insulin receptors on circulating red blood cells (RBC) showed abnormal inhibition-competition curves, characterized by increased percentage insulin binding at higher unlabelled insulin levels. Scatchard plots suggested an apparent increase in the number of low affinity receptors. Despite the changes in receptor-insulin interaction, the defect does not seem to explain the insulin resistance since binding of insulin to a target tissue (RBC) appeared to be quantitatively normal at physiological insulin levels, suggesting a simultaneous post receptor defect.