The Effect of Thyroid Disease in Pregnancy

What is Thyroid Disease

Thyroid disease is a disorder that affects the thyroid gland. Sometimes the body produces too much or too little thyroid hormone. Thyroid hormones regulate metabolism—the way the body uses energy—and affect nearly every organ in the body. Too much thyroid hormone is called hyperthyroidism and can cause many of the body’s functions to speed up. Too little thyroid hormone is called hypothyroidism and can cause many of the body’s functions to slow down.

Thyroid hormone plays a critical role during pregnancy both in the development of a healthy baby and in maintaining the health of the mother even after childbirth.

What is the thyroid?

The thyroid is a 2-inch-long, butterfly-shaped gland weighing less than 1 ounce. Located in the front of the neck below the larynx, or voice box, it has two lobes, one on either side of the windpipe. The thyroid is one of the glands that make up the endocrine system. The glands of the endocrine system produce, store, and release hormones into the bloodstream. The hormones then travel through the body and direct the activity of the body’s cells.

The thyroid gland makes two thyroid hormones, triiodothyronine (T₃) and thyroxine (T₄). T₃ is the active hormone and is made from T₄. Thyroid hormones affect metabolism, brain development, breathing, heart and nervous system functions, body temperature, muscle strength, skin dryness, menstrual cycles, weight, and cholesterol levels.

Thyroid hormone production is regulated by thyroid-stimulating hormone (TSH), which is made by the pituitary gland in the brain. When thyroid hormone levels in the blood are low, the pituitary releases more TSH. When thyroid hormone levels are high, the pituitary responds by decreasing TSH production.

How does hyperthyroidism (too much thyroid hormone) affect the mother and baby?

Uncontrolled hyperthyroidism during pregnancy can lead to:

• congestive heart failure
• preeclampsia—a dangerous rise in blood pressure in late pregnancy
• thyroid storm—a sudden, severe worsening of symptoms
• miscarriage
• premature birth
• low birth weight

How does hypothyroidism (too little thyroid hormone) affect the mother and baby?

Some of the same problems caused by hyperthyroidism can occur with hypothyroidism. Uncontrolled hypothyroidism during pregnancy can lead to

• preeclampsia (high blood pressure and high level of protein in pregnancy)
• anemia—too few red blood cells in the body, which prevents the body from getting enough oxygen
• miscarriage
• low birth weight
• stillbirth
• congestive heart failure, rarely

Blood Test for all Pregnant Women

This involves drawing blood at a health care provider’s office or commercial facility and sending the sample to a lab for analysis. Diagnostic blood tests may include

• TSH test.If a pregnant woman’s symptoms suggest hyperthyroidism, her doctor will probably first perform the ultrasensitive TSH test. This test detects even tiny amounts of TSH in the blood and is the most accurate measure of thyroid activity available.
  Generally, below-normal levels of TSH indicate hyperthyroidism. However, low TSH levels may also occur in a normal pregnancy, especially in the first trimester, due to the small increase in thyroid hormones from HCG.

• T₃and T₄ If TSH levels are low, another blood test is performed to measure T₃ and T₄. Elevated levels of free T₄—the portion of thyroid hormone not attached to thyroid-binding protein—confirm the diagnosis.
  Rarely, in a woman with hyperthyroidism, free T₄ levels can be normal but T₃ levels are high. Because of normal pregnancy-related changes in thyroid function, test results must be interpreted with caution.

• TSI test.If a woman has Graves’ disease (disease is an autoimmune disorder) or has had surgery or radioactive iodine treatment for the disease, her doctor may also test her blood for the presence of TSI antibodies.

For thyroid test, management and medication in pregnancy kindly visit your health care provider or consult the site specialist.

Reference

National Endocrine and Metabolic Diseases Information Service