Serum Leptin Level in Women with Polycystic Ovary Syndrome: Correlation with Adiposity, Insulin, and Circulating Testosterone

Background: Leptin, an adipocyte-derived hormone encoded by 'ob' gene, serves as a link relaying metabolic signals to the neuronal networks in the brain to modulate hypothalamo-pituitary-ovarian axis. Circulating leptin correlates strongly with obesity, which is frequently associated with polycystic ovarian syndrome (PCOS), a major form of dysovulatory infertility in women, characterized by endocrine abnormalities such as hyperandrogenism and inappropriate LH secretion. PCOS is also often associated with insulin resistance and hyperinsulinemia, features that are linked to leptin and its receptors. However, the relationship between leptin and gonadotropins, androgens, and insulin in PCOS is still controversial. Aim: Present investigation attempts to evaluate the interrelationship between serum leptin level with body mass index, insulin and with circulating testosterone in PCOS women. Subjects and Methods: Women diagnosed with either tubal block/male factor infertility (Control; n = 18) and with PCOS (n = 16), enrolled for in vitro fertilization and embryo transfer (IVF-ET), were recruited for this study. All were reviewed for body mass index (BMI), endocrine milieu (including pituitary gonadotropins, TSH, prolactin, gonadal steroids, and insulin) and for circulating serum leptin. Interpretation of data was done using PRISM Statistical Software Package (PRISM Version 4.03@1992-2005; GraphPad Software Inc). Results: Positive correlation was observed between serum leptin, BMI, and insulin in both the groups. Mean BMI, LH, and LH: FSH ratios were found elevated in the PCOS population. PCOS women also had significantly elevated androgens and fasting levels of insulin. Conclusion: Hyperleptinemia in PCOS women appears to be due to the positive correlation between serum leptin, BMI, and insulin.