Is levothyroxine safe during pregnancy?

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levothyroxine is a synthetic thyroid hormone approved by FDA for the treatment of hypothyroidism. Although obstetricians try to reduce the amount of drugs women take during pregnancy, levothyroxine is safe for pregnant women with hypothyroidism. In fact, the treatment of hypothyroidism is essential during pregnancy. Without treatment, hypothyroidism can lead to anemia, muscle pain, congestive heart failure and preeclampsia in pregnant women. It can also seriously affect the brain development of the fetus, leading to birth weight loss. During the first three months of pregnancy, the fetus is totally dependent on the mother's thyroid hormone. It is not until the second trimester of pregnancy that the fetal thyroid develops and the fetus produces its own hormones.

Sponsored Links: class <> a pregnant woman was sitting on the sofa with her hand. A glass of water and L-thyroxine. (picture: antonio_diaz/istock/getty images)

hypothyroidism and levothyroxine

The thyroid is a butterfly gland located in front of the neck, producing a hormone called thyroxine (t4). T4 is essential for many basic functions, such as metabolism, digestion, normal growth of hair and skin, and brain function. Hypothyroidism refers to insufficient T4 hormone secreted by the thyroid. Patients with hypothyroidism may experience fatigue, weight gain, dry skin, alopecia, constipation, memory loss, inattention and depression. In some countries, iodine deficiency leads to hypothyroidism. In the United States, when iodine is added to salt, people usually develop hypothyroidism because antibodies attack their thyroid glands. This condition is known as Hashimoto's thyroiditis. Hypothyroidism may also be caused by radiation, certain drugs and thyroid surgery. When the dose is too high, levothyroxine may cause side effects. These side effects are usually similar to hyperthyroidism, with palpitations, sweating, anxiety, diarrhea, fever, weight loss, abdominal pain and headache.

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Hypothyroidism and pregnant women should have thyroid examination immediately after pregnancy, and then every six to eight weeks during pregnancy. Thyroid stimulating hormone (tsh) and free T4 (ft4) are two recommended methods for thyroid examination in pregnant women. Patients with untreated hypothyroidism have high levels of thyrotropin, because pituitary gland releases thyrotropin when thyroid hormone is insufficient. FT4 is the content of free thyroxine in blood. In the blood, T4 is converted to t3, which is the active form of hormones. T3 and t4, which bind to proteins in the blood, are inactive. During pregnancy, the number of thyroid hormone binding proteins increases, resulting in a decrease in free T3 and T4 in the blood. To make up for this, levothyroxine doses usually have to be increased by 25% to 50% during pregnancy. Thyroid examination should be reexamined four weeks after dosage change until TSH is within the correct range.

There is a debate over whether all women, not just those who already have hypothyroidism or increased risk of hypothyroidism, should undergo TSH during pregnancy. Risk factors for hypothyroidism include family history, history of thyroid surgery or goiter. Pregnant women without these risks should still discuss the test with their doctors.

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