Feedback inhibition of insulin secretion and insulin resistance in polycystic ovarian syndrome with and without obesity

D. Sinagra, A.M. Scarpitta, M. BrigandÌ, G. D’acquisto

Istituto di Clinica Medica I, Divisione di Endocrinologia e Malattie del Ricambio, Policlinico Universitario “Paolo Giaccone” – Palermo, Italy

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• Endocrinology
• Internal Medicine

Hyperinsulinemia/insulin resistance is a well-known feature of polycystic ovarian (PCO) syndrome. In this study, the comparative roles of the peripheral tissues and the pancreatic beta-cells in its pathogenesis were evaluated. We determined basal serum C-peptide values (index of insulin secretion) and in vivo insulin action on peripheral glucose utilization (by the euglycemic hyperinsulinemic clamp technique) in obese (n=5) and nonobese (n=5) PCO women compared to obese (n=5) and nonobese (n=5) normal ovulatory women.

During the clamp, feedback inhibition of insulin on insulin secretion was studied by C-peptide percentage suppression. Serum C-peptide basal values did not differ significantly between the four groups. Insulin stimulated glucose utilization, expressed as M-value, was significantly decreased in both PCO groups compared to normal ovulatory women (p<0.005). The metabolic clearance rate of glucose (MCR) and insulin (M/I) had the same behaviour. No differences were found between M, MCR and M/I values and the two groups of PCO subjects (obese/nonobese). The C-peptide percentage suppression was similar in all the groups. We conclude that PCO women have a significant insulin resistance that is indipendent of obesity, while basal and insulin-inhibited insulin secretion do not differ from normal-cycle subjects.

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