INCREASED NUMBER OF IGF-I RECEPTORS ON ERYTHROCYTES OF WOMEN WITH POLYCYSTIC OVARIAN SYNDROME

OBJECTIVE To test the hypothesis that insulin acts though ovarian IGF- I receptors to produce excessive amounts of androgens in polycystic ov arian syndrome (PCOS), by measuring the binding capacity of IGF-I rece ptors on erythrocytes and relating the findings to the degree of hyper androgenism and hyperinsulinaemia. DESIGN A case-control study of IGF- I receptors on erythrocytes of women with PCOS and age and weight-matc hed controls, PATIENTS AND METHODS IGF-I receptors on erythrocytes, se rum levels of androgens, IGF-I, GH, basal insulin and insulin response during oral glucose tolerance test (oGTT) were measured after induced or spontaneous withdrawal bleeding in 10 women with PCOS and eight no rmo-ovulatory women, RESULTS An increased number of IGF-I receptors wa s found on erythrocytes of patients with PCOS compared with the contro ls (P < 0.01), irrespective of their body mass index, Serum IGF-I leve ls were similar in both groups, The degree of hyper-insulinaemia, prov oked by oGTT, correlated positively with basal insulin (r = 0.69; P = 0.003), but not with the number of IGF-I receptors, However, the numbe r of IGF-I receptors correlated positively with androstenedione (r = 0 .54, P = 0.0018). CONCLUSIONS The findings in the present study that t he number of IGF-I receptors and not the insulin levels correlate with serum androstenedione support the theory that the hyperandrogenism in PCOS is not a direct effect of the hyperinsulinaemia, but IGF-I media ted.