The thyroid makes two important hormones, triiodothyronine (T3) and thyroxine (T4). These hormones regulate a person's metabolism, the body's process of using energy. Metabolism affects practically every function of the human body [source: NEMDIS]. The function of the thyroid can affect a woman's ability to ovulate, thus making it harder to get pregnant. When the thyroid gland either produces too much thyroid hormone (hyperthyroidism) or too little (hypothyroidism), it can interrupt a woman's natural menstrual cycle. This in turn affects her ovulation cycle and can impede her ability to get pregnant [source: Mayo Clinic].