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Plasma interleukin 6 levels are elevated in polycystic ovary syndrome independently of obesity or sleep apnea.

Vgontzas AN, Trakada G, Bixler EO, Lin HM, Pejovic S, Zoumakis E, Chrousos GP, Legro RS

Sleep Research and Treatment Center, Department of Psychiatry H073, Penn State University College of Medicine, Hershey, PA 17033, USA. axv3@psu.edu

Premenopausal women with polycystic ovary syndrome (PCOS) are at a much higher risk for excessive daytime sleepiness, fatigue, and insulin resistance than control women. Elevated levels of interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) are presumably part of the pathogenesis of these clinical manifestations. Forty-two obese women with PCOS, 17 body mass index-comparable obese controls, and 15 normal-weight controls free from apnea participated in the study that included one 8-hour nighttime polysomnography, single morning cytokine plasma concentrations, and insulin resistance indices. Women with PCOS exhibited higher plasma concentrations of IL-6 than obese controls, who had intermediate values, or normal-weight controls, who had the lowest values (4.75 +/- 0.5 vs 3.65 +/- 0.4 vs 1.84 +/- 0.3 pg/mL, P < .01). Tumor necrosis factor alpha values were higher in PCOS and obese controls compared with normal-weight controls, but the difference was not statistically significant (4.05 +/- 0.3 vs 3.79 +/- 0.2 vs 3.14 +/- 0.2 pg/mL, P = .103). Based on backward regression analysis, IL-6 levels had a stronger association with the PCOS group than with the obese group, and the sleep or hypoxia variables did not make a significant contribution to either IL-6 or TNF-alpha. Both IL-6 and TNF-alpha correlated positively with body mass index (P < .01) in obese controls but not in women with PCOS. Furthermore, within the PCOS group, IL-6 and TNF-alpha correlated more strongly with indices of insulin resistance than obesity. We conclude that IL-6 levels are elevated in obese women with PCOS independently of obesity or sleep apnea and may represent a pathophysiologic link to insulin resistance.

Published 14 July 2006 in Metabolism, 55(8): 1076-82.
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