Study links obesity and type 2 diabetes to infertility in women

Insulin resistance - defined by persistently elevated levels of insulin and the abnormal regulation of blood sugar - is a common characteristic of type 2 diabetes. According to a recent study, it is also a feature of polycystic ovary syndrome (PCOS), which is the most common cause of infertility and affects up to one in 10 women.

Researchers at the Johns Hopkins Children's Center investigated the association between insulin resistance in obese women and infertility, suggesting that elevated levels of this hormone may potentially disrupt the pituitary gland.

"What we propose is a fundamentally new model showing that different tissues respond to obesity differently, and that while cells in the liver and muscle do become insulin resistant, cells in the pituitary remain sensitive to insulin," said lead researcher Andrew Wolfe.

They focused on pituitary cells called gonadotrophs, which secrete the luteinizing hormone (LH) needed for ovulation and fertility. The team hypothesized that high levels of circulating insulin may cause the gonadotrophs to pump out the LH and disrupt the process.

In the laboratory, they studied obese mice with missing insulin receptors. After three months on a high-fat diet, these mice maintained near-normal LH levels and regular ovulation, compared to animals with intact receptors.