Pituitary Sensitivity May Lead to Infertility in Obese Women

Mouse study finds gland's response to insulin could set off fertility-diminishing reactions
By Monica Smith
HealthDay Reporter

FRIDAY, Sept. 10 (HealthDay News) -- Infertility in obese women may be due to the ovarian-disrupting response of the pituitary gland to high insulin levels, according to a mouse study published in the Sept. 8 issue of Cell Metabolism.

To determine the impact of obesity on reproductive tissues, Kathryn J. Brothers, of the Johns Hopkins University School of Medicine in Baltimore, and colleagues compared mice engineered with missing insulin receptors in their pituitary glands to mice with intact insulin receptors.

The researchers found infertility and an increase in luteinizing hormone after gonadotropin-releasing hormone or insulin stimulation in wild type mice with diet-induced obesity. Mice with a pituitary knockout of the insulin receptor, however, were capable of reproduction regardless of being lean or obese.

"In summary, these findings indicate a direct role for insulin signaling in the gonadotroph that is revealed in an obesity model of infertility. When wild type mice became obese, they showed metabolic and reproductive profiles similar to women with hyperinsulinemia and fertility deficiencies such as polycystic ovarian syndrome. When the insulin receptor was ablated in the gonadotroph, obese pituitary-specific insulin receptor knockout mice displayed an improvement in reproductive function, implicating pituitary insulin signaling in the genesis of obesity-induced infertility," the authors write.

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