The insulin resistant subphenotype of polycystic ovary syndrome: clinical parameters and pathogenesis.

Objective: This study was undertaken to compare clinical and biochemical characteristics of the insulin resistant (IR) and non-IR subphenotypes of polycystic ovary syndrome (PCOS).

Methods: Infertile PCOS women were classified as IR (n=32) or non-IR (n=46) on the basis of fasting glucose and insulin levels. The incidence of acanthosis nigricans (AN), hirsutism, and ovulation in response to clomiphene citrate (CC) was compared between the 2 groups, along with serum levels of gonadotropins, and sex steroids. Blood samples from 28 PCOS patients and 8 controls were analyzed by enzymatic immunoassay for autophosphorylated insulin receptor (APIR) and total insulin receptor (TIR) content.

Results: Insulin resistance was associated with obesity (odds ratio [OR]=3.5, P <.05), AN (OR=6.0, P <.05), hirsutism (OR=3.1, P <.05), and resistance to CC (OR=5.0, P <.05). Mean levels of LH, LH/FSH ratios, and testosterone were lower in women with IR (11.5 +/- 6.8 mIU/mL, 2.0 +/- 1.0, and 56.6 +/- 29.0 ng/dL, respectively) compared with women without IR (15.0 +/- 13.4 mIU/mL, 2.4 +/- 1.5, and 72.5 +/- 29.8 ng/dL, respectively) (P <.05). Mean APIR/TIR ratios in IR women were lower than in non-IR women (P <.05 at 100 nmol/L of insulin) and controls (P <.01 at 1, 10 and 100 nmol/L insulin).

Conclusions: Patients with IR are more likely to be obese and have AN, hirsutism, resistance to CC, and lower LH, LH/FSH ratios, and testosterone levels. Furthermore, IR patients appear to have defective autophosphorylation of the insulin receptor, a key element in insulin action, and a possible mechanism for IR in PCOS.