Retinol-binding protein in nonobese women with polycystic ovary syndrome

Relationship of obesity-related disturbances with LH/FSH ratio among post-menopausal women in the United States

OBJECTIVES

Although luteinizing hormone to follicular stimulating hormone (LH/FSH) ratio is a controversial criterion for identifying a sub-group of infertile women with polycystic ovary syndrome (PCOS) and abnormalities at the level of the hypothalamic-pituitary-ovarian axis, an elevated LH/FSH ratio is frequently observed in PCOS cases. Obesity and insulin resistance are highly prevalent among PCOS women. To date, no studies have examined the associations of LH/FSH ratio with these co-morbid conditions outside the context of pre- and peri-menopausal PCOS women. The objective of this study is to evaluate whether the LH/FSH ratio is associated with obesity, insulin resistance, metabolic disturbances and chronic inflammation among post-menopausal U.S. women, 35-60 years of age.

STUDY DESIGN

Cross-sectional study of 693 women who participated in the 1999-2002 National Health and Nutrition Examination Survey.

MAIN OUTCOME MEASURES

Body mass index, waist circumference, triglycerides, high-density lipoprotein (HDL) cholesterol, systolic and diastolic blood pressures, fasting glucose, metabolic syndrome, Homeostasis Model Assessment for Insulin Resistance and C-reactive protein (CRP).

RESULTS

Age- and hysterectomy-adjusted regression models suggest that CRP level is positively associated with LH/FSH ratio and LH/FSH>1, high glucose level and LH/FSH>2 are inversely related and HDL<50mg/dL is positively associated with both LH/FSH>1 and LH/FSH>2.

CONCLUSIONS

In a nationally representative sample of post-menopausal women, markers of chronic inflammation and dyslipidemia which are characteristics of PCOS-associated morbidities were also significantly associated with LH/FSH ratio, meriting further investigation.

The relationship between retinol-binding protein 4 levels, insulin resistance, androgen hormones and polycystic ovary syndrome

BACKGROUND

Retinol-binding protein 4 (RPB4), a 21-kDa peptide, is a recently identified adipokine that may contribute to the pathogenesis of polycystic ovary syndrome (PCOS). The aim of this study was to explore the association between serum RBP4 levels, androgen hormones and insulin resistance (IR) in women with PCOS.

METHODS

In this case-control study, 75 PCOS patients and 53 age- and body mass index (BMI)-matched control subjects referred to the Zanjan Metabolic Disease Research Center were enrolled. Serum RBP4 was measured using an enzyme-linked immunosorbent assay. BMI, waist circumference (WC), fasting levels of glucose, lipid profiles and insulin were also measured. A homeostatic model assessment of insulin resistance (HOMA-IR) value was used to determine the level of insulin resistance.

RESULTS

PCOS cases had significantly higher serum RBP4 and insulin levels than control subjects (44130 ± 12760 vs. 32980 ± 9560 μg/L, p < 0.001, and 11790 ± 11480 vs. 7890 ± 4300 μU/L, p < 0.05, respectively), in univariable analysis. RBP4 showed a positive correlation with serum testosterone (r = 0.62, p < 0.0001), dehydroepiandrosterone sulfate (r = 0.45, p < 0.0001) and the waist circumference (r = 0.37, p < 0.001) of PCOS patients but not with other measured clinical and biochemical variables. However, no correlation was observed between serum RBP4 levels and HOMA-IR in all studied subjects. A final logistic regression analysis demonstrated that testosterone and dehydroepiandrosterone sulfate are independently associated with PCOS.

CONCLUSION

These findings indicate that RBP4 is not independently associated with PCOS. The elevation of RBP4 levels in PCOS women might be influenced by androgen hormones. Further prospective studies are needed to clarify molecular mechanisms.