Thyroid Disease During Pregnancy
Thyroid disease occurs when the thyroid gland malfunctions and produces an abnormal quantity of hormones. When a malfunctioning thyroid gland produces too much or too little hormone during pregnancy, abnormal hormone secretion can be damaging not only to the mother, but to the developing fetus as well. This is because thyroid hormone is essential to the development of the fetal brain and nervous system and, until about 12 weeks into gestation, the fetus depends on its mother's supply of thyroid hormone.
The two thyroid hormones, triiodothyronine and thyroxine, help to regulate a great many bodily processes, including:
- Brain development
- Cholesterol levels
- Heart rate
- Metabolism and weight
- Nervous system functions
- Muscle strength
- Menstrual cycles
- Body temperature
Two pituitary hormones active during pregnancy, human chorionic gonadotropin (hCG) and estrogen, normally result in increased secretion of thyroid hormones, so thyroid abnormalities may be difficult to diagnose at this time. Women who have a family history of thyroid difficulties, or who have had any thyroid issues in the past, should be carefully monitored.
Types of Thyroid Disease During Pregnancy
There are two primary types of thyroid disease that occur during pregnancy: hyperthyroidism and hypothyroidism. Either disorder, although diagnosed during pregnancy, may have been a pre-existing condition.
Hyperthyroidism is the condition that occurs if the thyroid is too active, producing excessive levels of thyroid hormones. During pregnancy, hypothyroidism is usually caused by Graves' disease, an autoimmune condition. Symptoms of hyperthyroidism may include:
- Hyperactivity, nervousness, irritability
- Rapid or irregular heartbeat
- Increased sensitivity to heat
- Excessive sweating
- Weight loss or failure to gain normal pregnancy weight
- More frequent bowel movements
- Muscle weakness
- Eye bulging or irritation
Rarely, patients with Graves' disease also develop a condition known as hyperemesis gravidarum, that results in severe nausea and vomiting.
Hypothyroidism is the condition of an underactive thyroid. Symptoms of hypothyroidism during pregnancy may include:
- Excessive weight gain
- Increased sensitivity to cold
- Dry skin
- Joint and muscle aches
- Muscle weakness
During pregnancy, hypothyroidism is typically caused by Hashimoto's disease, an autoimmune disorder that causes chronic inflammation of the thyroid gland.
For some women, there may be a link between hypothyroidism and infertility. Low levels of thyroid hormone can interfere with ovulation, which can impair fertility.
Diagnosis of Thyroid Disease During Pregnancy
Both hyperthyroidism and hypothyroidism are diagnosed during pregnancy by assessing physical symptoms, administering thyroid function tests, and taking blood tests to measure hormone levels.
Treatment of Thyroid Disease During Pregnancy
Pregnant patients with hyperthyroidism may be treated with a medication to slow production of thyroid hormones and will be required to restrict their dietary intake of iodine. The radioactive iodine normally used to treat hyperthyroidism cannot be administered to pregnant women because it is dangerous to the fetal thyroid gland. In rare cases, where patients are unable to tolerate the anti-thyroid medication, surgery to remove part or all of the thyroid gland may be performed.
Pregnant patients with hypothyroidism are treated with synthetic thyroid hormone in order to restore proper levels of thyroid hormone. In both types of thyroid disease during pregnancy, medications will be administered in the smallest possible doses because of their potential affect on the fetus.
Complications of Thyroid Disease During Pregnancy
It is essential that thyroid disease be controlled during pregnancy because untreated it may result in several serious risks to the mother or newborn, including:
- Heart failure
- Miscarriage or premature birth
- Low birth weight, poor weight gain
- Early closure of the soft spot in the infant's skull
Uncontrolled thyroid disease may also lead to an ailment known as a "thyroid storm," a sudden severe exacerbation of symptoms characterized by high fever, abnormal blood pressure, vomiting, extreme fatigue, breathing difficulties, delirium and shock. Thyroid storm is a life-threatening condition.