A 26 year old, newly-pregnant woman sits on the exam table in her obstetrician’s office. She is excited about her pregnancy and does not want to complain about her nausea, vomiting, weight loss, anxiety, difficulty sleeping, and fatigue. The obstetrician can tell just by looking at her that she seems to be suffering the normal symptoms of pregnancy and is not overly worried. After all, nausea and vomiting occur in 50-80% of all pregnant women, especially between the 5th and 13th week. The doctor reassures the patient that this is normal, and encourages her to hydrate and rest. Sometimes the physician will suggest a medication, or a supplement, to reduce the symptoms of nausea and vomiting.
Is it possible that this woman is experiencing something more severe than the normal, early pregnancy symptoms?
One of the great masqueraders for pregnant women is thyroid disease. Many of the symptoms that women experience in the early stages of pregnancy are the exact symptoms that occur with thyroid problems. Women will commonly experience fatigue, weight gain, constipation, insomnia, and lethargy. Health care providers will often reassure patients that this is normal and these symptoms are due to the hormonal and physiological changes that one expects with the early stages of a healthy pregnancy. However, one must be on the alert that these same symptoms could be representative of a much more serious underlying problem; one that could have major, negative ramifications on the pregnancy and the newborn infant. Left undiagnosed and untreated, hypothyroidism (low thyroid hormone) could result in serious, high-risk conditions during the pregnancy. Prematurity, preeclampsia, placental separation (abruption), and/or serious consequences in the child such as congenital cretinism (mental retardation, deafness, muteness).
This weeks article will focus only on hy-PER-thyroidism (when you have too much thyroid hormone.)
Next week we will review hyp-O-thyroidism. (when you have too little thyroid hormone) and its effects on pregnancy.
Who should get screened for thyroid disease in pregnancy?
The current American College of Obstetrics and Gynecology guidelines state that thyroid functions should be checked only in women with a personal history of thyroid disease or symptoms of thyroid disease. It is NOT universally recommended to test all pregnant women even though there are cases of women who have disease that do not have symptoms (subclinical cases).
How does maternal thyroid hormone effect the fetus?
The fetal brain is completely dependent on maternal thyroid hormone until about 12 weeks gestation. At that time, the fetus is able to manufacture its own thyroid hormone in conjunction with the maternal hormone that crosses the placenta. Diminished levels of thyroid hormone in the mother impair fetal brain development. Elevated levels can also cross the placenta and cause excessive production in the fetus. (Graves disease.)
What is hyperthyroidism?
The thyroid is an endocrine gland located in the neck that controls metabolism. It receives a message (TSH) from an area in the brain called the pituitary which releases thyroid hormone (T4).
When the gland produces more hormone than it is supposed to, hyperthyroidism is diagnosed (elevated thyroid hormone T4 and low TSH.) This can occur in about.2% of all pregnancies. The most common form of the disease is Graves disease where certain antibodies are made by the body that stimulate thyroid hormone production. Other causes can be multinodular goiter, subacute thyroiditis, an extra thyroid source of hormone production (certain tumors of the ovary or pituitary), thyroid adenoma.
What are the symptoms of hyperthyroidism?
- frequent stool
- excessive sweating
- heat intolerance
- weight loss
- eye changes-lagging of the eyelid and retraction of the eye lid
What are the risks to the mother and the fetus if hyperthyroidism is left untreated?
If left untreated, hyperthyroid can cause:
- preterm delivery
- severe preeclampsia
- heart failure
- fetal loss
- low birth weight infants
- fetal hyperthyroidism
How do you treat hyperthyroidism in the mother?
A classification of drugs called thioamides are used to treat hyperthyroidism.
These drugs prevent the manufacture of the thyroid hormone by preventing a needed substrate iodine from attaching to the thyroid molecule and it also blocks the the manufacture of of another active form of the hormone T3.
These drugs do cross the placenta and can effect the fetal thyroid, although it is generally transient. Generally, these drugs are safe to use in pregnancy but rare side effects of the drug can include fever, sore throat, hepatitis, rash, nausea, loss of taste and smell, loss of appetite and a very serious and rare side effect called agranulocytosis (less than 1%) which is an abnormal condition of the blood characterized by a severe reduction of white blood cells (fever, prostration and bleeding ulcers of rectum, mouth, and vagina.)
Infants must be observed carefully after birth with mothers on antithyroid medication since newborns have been known to have neonatal hypothyroidism and goiter in mothers who have been treated. Babies are ultrasounded during pregnancy looking for fetal goiter and growth problems which can present problems at delivery due to the hyperextension of the neck.
It is generally considered safe to breast feed on these medications.
Other drugs used to treat hyperthyroidism are beta-blockers (propranolol) which act to reduce the rapid heart rate that can occur. Side effects from this drug can include growth retardation in the fetus, fetal bradycardia (slowed heart rate) and hypoglycemia in the infant (low blood sugar).
Radioactive iodine is never used in pregnancy since it can ablate the fetal thyroid. A patient was treated with radioactive iodine prior to becoming pregnant, should avoid becoming pregnant for at least 4 months. If all medications fail, or allergy to the medications exist, thyroidectomy, or surgical excision of the thyroid is recommended.
What is subclinical hyperthyroidism?
In about 1.7% of women there are asymptomatic women with normal thyroid hormone but a low TSH. This condition generally has been found to have no effect on the pregnancy since it is the maternal T4 level that is critical for fetal brain development, regardless of what the TSH level is. However, these women should be observed for osteoporosis, cardiovascular morbidity and progression to overt disease or thyroid failure in the future.
What is thyroid storm?
Thyroid storm is an acute obstetrical emergency that occurs in about 10% of women with hyperthyroidism. Symptoms include a change in mental status, seizures, nausea, diarrhea, and cardiac arrythmias. Patients are placed in the intensive care unit for constant monitoring and observation since there is a high risk of maternal heart failure. Thyroid storm can be precipitated by an acute surgical emergency, infection, diabetes. anesthesia, and noncompliance with thyroid medications. In addition to the usual treatment of hyperthyroidism as described above, steroids are commonly given.
Can thyroid disease present itself right after delivery?
About 6 to 9% of women with no history of thyroid disease can present with disease after delivery, generally within the first year postpartum. This is common in women that have previously known thyroid antibodies that are not activated until after the delivery, or women with a strong family history of diabetes or other autoimmune disorders. Most women have transient hyperthyroidism which then converts to hypothyroidism requiring treatment. About 77% of women will completely recover but 30% will continue with thyroid disease permanently. Many women that recover will develop this disorder again with subsequent pregnancies.
Because of the close similarity of symptoms that occur with a normal early pregnancy, be sure to ask your health care providers if you should be screened for thyroid disease. Discovery and correction of this condition can have beneficial ramifications to ensure a happy, healthy mother and baby. As stated in many previous articles, pregnancy can be the crystal ball of future medical conditions and by being vigilant, pregnancy can help a woman avoid diseases and conditions from surfacing later in life.