Why obesity causes infertility

Scientists say they've figured out why obesity and infertility go hand in hand.

"There was a sense that the reproductive dysfunction was due to insulin resistance. 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 become insulin resistant, cells in the pituitary remain sensitive to insulin," Andrew Wolfe of Hopkins Children's was quoted as saying.

According to Wolfe, infertility occurs when insulin-sensitive pituitary cells get flooded with the rising insulin levels that are so common in obesity. The pituitary gland is at the base of the brain. Special cells in the gland produce hormones that control ovulation and fertility.

In an experiment using mice, lean mice with or without pituitary insulin receptors had six times the number of successful pregnancies compared to otherwise normal obese mice. The obese mice with missing pituitary insulin receptors fared almost as well; they had five times more successful pregnancies than typical obese mice.

Wolfe say he would still like to work out exactly what it is that's different about the pituitary insulin receptors, and the role of those receptors found in ovarian cells.