1.What is the thyroid gland and what is its function? The thyroid gland is a double-lobed, butterfly shaped gland located in the neck. It produces two types of hormones, thyroxin (T4) and triiodothyronine (T3), that are necessary for proper metabolism. The production of these hormones is controlled by thyroid-stimulating hormone ( TSH ). TSH is released by the pituitary gland (a gland in your brain). Thyroid hormones are circulating in bloodstream in free and bound to protein (TBG) state.
2.What causes thyroid disease? Sometimes thyroid gland secretes too much or two little thyroid hormone, that can lead to thyroid diseases. Thyroid diseases are eight times more common in women then in men.
3.Who should be screened for thyroid disease during pregnancy? Thyroid disease often manifests itself during the reproductive period of a woman’s life and is the second most common endocrinopathy that affects women of childbearing age. Universal screening for thyroid disease is not recommended at this time. Screening is appropriate if there are symptoms of thyroid disease or history of thyroid disease. Thyroid nodule or goiter should be evaluated.
4.How is thyroid disease diagnosed during pregnancy? In pregnancy the values of thyroid hormone blood levels change significantly due to changes in pregnancy hormones (b-hCG and estradiol). The physiologic changes of pregnancy can mimic thyroid disease. Pregnancy may stimulate remission or exacerbation of thyroid disorders.
History, physical exam, levels of TSH , T4 and T3 in blood, as well as thyroid scan and thyroid ultrasound can help establishing the diagnosis.
5.Is increase in thyroid gland size normal during pregnancy? Requirements for iodine increase during pregnancy due to fetal iodine use and increased clearance of iodine by kidneys. In 15 % of pregnant women this is associated with a noticeable increase in thyroid gland size, which returns to normal after delivery. Thyroid function tests are normal.
Goiter is abnormal and needs further investigation.
The World Health Organization recommendation is 200 micrograms/day of iodide for pregnant women.
6.What is hypothyroidism and how does it affect pregnancy? Hypothyroidism is a disease when body does not make enough thyroid hormone. The most common causes in pregnancy are chronic thyroiditis (inflammation of the thyroid gland) and chronic autoimmune thyroiditis (Hashimoto’s disease). Other causes might be prior radioactive iodine therapy, removal of thyroid gland, and iodine deficiency.
Associated symptoms include fatigue, weight gain, constipation, decreased pulse rate, cold intolerance, diminished reflexes, goiter (an enlarged thyroid gland), dry skin, dry hair, hair loss, brittle nails, depression, decreased libido, muscle aches, swelling of eyelids, hands and feet. If untreated, hypothyroidism can proceed to coma.
Elevated blood TSH levels with no rise in T4 is suggestive of hypothyroidism.
Hypothyroidism is called subclinical when thyroid hormone changes are not accompanied by clinical symptoms. Mothers and babies are usually doing well and no treatment is needed unless the cause is iodine deficiency.
7.How can hypothyroidism be treated during pregnancy? The drug levothyroxine, which is synthetic T4, can be safely taken during pregnancy and breastfeeding. Since pregnancy increases need for thyroid hormone, the dosage should be carefully adjusted by the doctor.
8.What is hyperthyroidism and how does it affect pregnancy? Hyperthyroidism is a condition in which a body makes too much thyroid hormone. It affects 0.2 percent of pregnancies. The most common cause is Graves ‘s diseases (antibodies against thyroid gland stimulate excessive production of thyroid hormone). Theses antibodies can cross placenta and cause neonatal Grave’s disease. One of the signs of Graves ‘s disease is prominent, bulging eyes.
Hyperthyroidism shares some symptoms with pregnancy and is commonly associated with palpitations and rapid heart rate, nervousness and anxiety, enlarged thyroid gland, weight loss or gain, increased appetite, frequent loose bowel movements, heat intolerance, increased perspiration, insomnia, fatigue, tremors, shoulder and thigh weakness, prominent eyes, lower leg swelling, nail changes, hair loss, oily skin, emotional changes and increased libido.
Thyroid function tests should differentiate thyroid disease from normal pregnancy.
> Test Normal Pregnancy Hyperthyroidism|
> TSH No change Decreased
> TBG Increased No change
> Total T4 Increased Increased
> Free T4 No change Increased
> Total T3 Increased Increased
> Free T3 No change Increased
> Thyroid radio-iodine uptake Increased Increased
> T3RU Decreased Increased
9.How is hyperthyroidism treated during pregnancy? Hyperthyroidism can be treated with antithyroid drugs.
Radioactive thyroid treatment is contraindicated during pregnancy. The goal of treatment is to keep the patient with the free T4 in the upper limit of normal range so as not to cause fetal or neonatal hypothyroidism (T4, T3 and thyroid medications cross the placental barrier, TSH does not).
Both PTU ( propylthiouracil) and methimasole can be used in treatment of maternal hyperthyroidism. Recent studies have found no increased rates of fetal anomalies for both agents. Women treated with PTU or methimasole can breastfeed safely.
Agranulocytosis ( changes in the blood smear as a side effect of these medications ) can present with sore throat and fever, in which case immediate consultation with the physician and discontinuation of medication is warranted.
10.What is thyroid storm and how is it treated? Thyroid storm (fever, increased and irregular heart beat, altered mental status, diarrhea) is an extreme manifestation of the hyperthyroidism. It affects 1 % of pregnant women and is a medical emergency. Supportive care and appropriate medication therapy are important. Unless necessary, delivery should be avoided.
11.What are the pregnancy complications of untreated hypo- and hyperthyroidism? Risks are preeclampsia, miscarriage, preterm delivery and maternal heart failure.
12.What are the risks for the baby? Thyroid hormones are important in fetal brain development. Both hypo- and hyperthyroidism can cause low birth weight. Fetal thyrotoxicosis should be considered in women with Graves ‘s disease. The antibodies against thyroid gland cross the placenta and can cause fetal hyper- or hypothyroidism. Maternal hypothyroidism from iodine deficiency increases the risk of congenital cretinism (growth failure, mental retardation).
There is universal screening for congenital hypothyroidism in United States and prompt treatment can prevent sequelae. Consultation with the high-risk specialist is extremely important for women with thyroid disease for favorable pregnancy out come for both mother and neonate.
13. What is postpartum thyroiditis? Postpartum thyroiditis is an inflammation of the thyroid gland that follows delivery, and is not painful. It is often undiagnosed because symptoms, such as nervousness, fatigue, weight loss, and emotional changes are often thought to be a part of the normal postpartum recovery.
It is important for women who are experiencing postpartum depression to have their thyroid hormone levels checked.