THYROID DISEASE & FERTILITY
Thyroid disease is common in reproductive age women and observed at an incidence of approximately 1%. Both hyperthyroidism (increased activity) and hypothyroidism (decreased activity) can be associated with reproductive problems. The most common problem encountered with thyroid disease related to reproduction is a dysfunction in ovulation.
Most patients with hypothyroidism will not ovulate and have infertility, but some may ovulate irregularly and conceive spontaneously. If maternal hypothyroidism is untreated in pregnancy, it may have significant adverse effects on the fetus, such as mental and physical disability. Hyperthyroidism can also result in ovulatory dysfunction and eventually infertility, with other adverse effects if left untreated.
Hypothyroidism is defined as high thyroid stimulating hormone level (TSH) and low thyroid hormones (T3 and/or T4). Hypothyroidism can cause ovulation problems, infertility and is also associated with recurrent pregnancy loss. It is believed that hypothyroidism is due to an autoimmune reaction, and when goiter (enlargement of the thyroid gland) is present, it is called Hashimoto’s thyroiditis. Some of the symptoms of hypothyroidism are cold intolerance, constipation, low energy, fatigue, water retention, slow speech, but in some cases patients may be totally asymptomatic.
Subclinical hypothyroidism is defined as an elevated TSH level with normal thyroid hormone concentrations (T4). This phenomenon can be associated with reproductive problems as well as metabolic abnormalities. Patients with subclinical hypothyroidism are at an increased risk of developing overt hypothyroidism and some believe that these patients should be treated the same as patients with hypothyroidism.
Hyperthyroidism is defined as a suppressed/low TSH level and elevated thyroid hormones (T3 and/or T4). Two primary causes of hyperthyroidism are Graves’ disease (toxic diffuse goiter) and Plummer’s disease (toxic nodular goiter). Plummer’s disease is usually encountered in postmenopausal women who have had a long history of goiter. Graves’ disease is defined as hyperthyroidism, exophthalmus (protrusion of eyes) and pretibial myxedema (swelling in the legs), and is believed to be caused by auto-antibodies. Common symptoms include nervousness, heat intolerance, weight loss, sweating, palpitations, warm-moist skin and goiter (enlargement of thyroid gland).
Subclinical hyperthyroidism is defined as normal thyroid hormone levels and a low TSH level. This condition can be associated with bone loss and atrial fibrillation and therefore needs treatment to prevent cardiac complications and fractures. Progression to overt hyperthyroidism is uncommon, unlike subclinical hypothyroidism.
Whether thyroid disease is overt or subclinical, low or high, it can have significant impact on reproduction and pregnancy outcome. It is recommended that thyroid disease screening be done in patients at high risk of having the disease, who are symptomatic, have a significant medical history of autoimmune diseases, history of recurrent pregnancy loss, have ovulation problems or with the presence of thyroid gland enlargement on examination.
Hypothyroidism is commonly treated with levothyroxine (Synthroid, Lovolet, Levoxyl, L-Thyroxine) and hyperthyroidism with propylthiouracil (PTU) or methimazole (Tapazole). Treatment should be started before pregnancy to improve outcome and minimize obstetrical complications. TSH and thyroid hormone levels are checked at regular intervals to sustain normal thyroid function. Thyroid hormone requirement increases in pregnancy and the dose of supplemental thyroid hormone needs to be increased in patients with hypothyroidism. Close follow up and adequate treatment will optimize outcome.
We screen patients for thyroid disease and recommend treatment based on the type of the disorder. Once thyroid disease is under good control, patients can attempt to conceive spontaneously or by using assisted reproductive technologies.