Hypothyroidism (or underactive thyroid) occurs when the thyroid gland doesn’t produce enough hormones. Low levels of thyroid hormone can interfere with ovulation and affect fertility. Severely overactive thyroid, or hyperthyroidism, is less common but can also cause fertility problems.
If you suspect your thyroid may be interfering with your ability to get pregnant, ask your doctor for a blood test to assess your thyroid-stimulating hormone (TSH) levels. “Today’s tests are very advanced and can sometimes detect a problem before any symptoms appear,” says Dr. Afshan Zahedi, medical director of the Thyroid Program at Women’s College Hospital in Toronto. (Symptoms of hypothyroidism include sudden weight gain, dry skin, chills, muscle aches and fatigue, while symptoms of hyperthyroidism include sudden weight loss, sweating, anxiety and rapid heartbeat.)
How iodine fits in
“Iodine is necessary for thyroid function, but getting enough usually isn’t a problem,” says Zahedi. Most of us get plenty from our diet in foods like beans, grains, nori and dairy — and getting too much can actually cause thyroid problems. If you’re trying to get pregnant, Zahedi recommends taking a prenatal vitamin that contains the recommended iodine dose of 150 to 200 micrograms (this goes up to 220 mcg if you’re already pregnant).
Left untreated, hypothyroidism increases your risk of infertility, as well as miscarriage, premature delivery and pre-eclampsia if you’re already pregnant. Most doctors prescribe a daily dose of the synthetic thyroid hormone levothyroxine to restore hormone levels. Treatment with levothyroxine is usually lifelong, but side effects are few, and the treatment is relatively inexpensive. Because the dosage you need may change, your doctor should check your TSH level every year.