Mary, who has subclinical hypothyroidism, wondered whether some of the mental disabilities of her daughter were caused by her condition when she was pregnant. Hypothyroidism and hyperthyroidism are disorders of the thyroid gland. The thyroid gland is a butterfly-shaped gland right below the larynx on the neck and produces the thyroid hormones T3 and T4. These hormones control your body's metabolism, including body temperature and weight, muscle and bone strength, and brain development. A pregnant mother's untreated hypothyroidism or hyperthyroidism cause abnormal thyroid function, which can affect the baby. Sometimes abnormal thyroid function can develop during pregnancy.
Normal thyroid function in pregnancy
Normal development of the baby's brain during the first 10 to 12 weeks of pregnancy requires the mother's thyroid hormones. After this time period, the baby can manufacture its own thyroid hormones. A normal pregnancy induces changes in the mother's metabolism, which can make it more difficult to diagnose hypothyroidism or hyperthyroidism.
1. Increased thyroid hormones
Estrogen and pregnancy hormones increase the concentration of thyroid hormones in the pregnant mother. It is important that you take in enough iodine, if you are pregnant, so that the thyroid gland can make sufficient thyroid hormone. Iodine is needed to produce thyroid hormones. Use iodized table salt to get enough iodine in your diet.
2. Enlarged thyroid gland
The thyroid gland increases in size during pregnancy to provide enough thyroid hormone for the baby. The increase in size is not large enough that it can be detected by just touch. If your thyroid gland is noticeably enlarged, it may indicate a thyroid disorder.
Hypothyroidism in pregnancy
In hypothyroidism, the thyroid gland does not make sufficient amounts of thyroid hormone. An existing condition can cause hypothyroidism or it can arise during pregnancy due to Hashimoto's disease. Hashimoto's disease is an autoimmune disorder, where the body's own immune system attacks the thyroid gland. One to three cases due to Hashimoto's disease occur in every 1,000 pregnancies, according to the National Endocrine and Metabolic Diseases Information Service. Untreated hypothyroidism during pregnancy can cause miscarriages, stillbirths, and developmental brain defects in the baby. See a physician if you develop the symptoms of hypothyroidism.
1. Cold intolerance
Cold intolerance is a symptom of hypothyroidism and differs from other thyroid disorders.
2. Extreme fatigue
Fatigue in pregnancy is normal and may also be caused by other factors, but extreme fatigue together with other symptoms should be checked out.
3. High TSH, low free T4
A blood test can tell if you have high levels of TSH (thyroid stimulating hormone), a symptom of hypothyroidism. T4 (thyroxine) is the thyroid hormone that controls the metabolism of your body and you need to treat low T4 during your pregnancy. If you have high TSH, but normal amounts of T4, you have subclinical hypothyroidism, a mild form of the disorder. Two to three percent of pregnant women have subclinical hypothyroidism. It is not known if subclinical hypothyroidism can adversely affect the baby.
Hyperthyroidism in pregnancy
Hyperthyroidism is a thyroid disorder, characterized by the production of excessive amounts of thyroid hormone by the thyroid gland. Hyperthyroidism may exist prior to a pregnancy or it can develop during pregnancy. Hyperthyroid symptoms during pregnancy are difficult to identify, because the hyperthyroid symptoms resemble those of a normal pregnancy. Development of hyperthyroidism during pregnancy is usually caused by Graves disease. Graves disease is an autoimmune disease, where the body makes an antibody that mimics TSH. This antibody stimulates the thyroid gland to make more thyroid hormone.
1. Heat Intolerance
Heat intolerance can be a symptom of hyperthyroidism or of a normal pregnancy.
2. Heart Rate
Rapid and irregular heart beat indicates hyperthyroidism. A mother's hyperthyroidism can cause the baby's heart to beat faster and irregular, called tachycardia. This is a danger sign and can result in a stillbirth and even congenital malformations.
3. High TSH
High levels of TSH in the mother can affect the baby's thyroid and cause hyperthyroidism in the baby. By taking anti-thyroid medication, you can avoid the effect on your baby.