At the very first visit that I see a couple suffering from infertility, one of the first blood tests I order is a thyroid level, specifically, thyroid hormone levels. The thyroid gland, present in the neck, is very important in setting the metabolism for the body. The thyroid gland also, unbeknownst to many women, is very involved in your rate of ovulation. When the thyroid gland is under-active, which we call "hypothyroidism," many women do suffer from ovulation dysfunction. Many women with hypothyroidism will get their periods only a few times per year.
They also experience other symptoms, like weight gain or constipation, or feeling very cold when other people feel comfortable or even warm. It's very important, also, to control a woman's weight for infertility. And women who have hypothyroidism often gain weight at very high rates, and now have an obesity factor or just an overweight factor which contributes to some of the aberrations in their hormone levels. It's very important, also, that the thyroid levels be kept in check, because women with hypothyroidism also have a much higher rate of miscarriage or an early pregnancy loss. So, determining optimal levels of thyroid function are paramount to the success of couples undergoing infertility treatment.