How can pregnancy lead to hypothyroidism

Thyroid and pregnancy

The most important thing for the optimal development of the unborn child is a healthy mother. Impaired maternal thyroid function during the first few weeks of pregnancy can cause problems in the child during the first few years of life and perhaps even throughout life.

Even in the healthy thyroid gland, there are significant changes during pregnancy. The organ increases in volume a little. Excessive, pathological enlargement, however, indicates a thyroid problem that needs to be clarified in detail.

Thyroid dysfunction (too much or too little thyroid hormones) usually does not occur during pregnancy. The concentration of thyroid hormones can, however, deviate slightly from the normal ranges that relate to "non-pregnant women".

The need for iodine is increased, so that at least 200 µg iodine per day should be taken with food. The placenta produces a hormone called chorionic gonadotropin, which also has a stimulating effect on thyroid hormone production. Overall, pregnancy places increased demands on the thyroid gland that healthy people can easily cope with. In women with clinically silent thyroid diseases, these increased requirements during pregnancy can lead to a manifest disease.

The main thyroid diseases during and immediately after pregnancy are

  • the hypothyroidism
  • the hyperthyroidism
  • the goiter (diffuse and / or nodular enlargement of the thyroid gland)
  • the "postpartum" thyroiditis

Underactive thyroid (hypothyroidism)

Too little thyroid hormone is called underactive or hypothyroidism. The reasons are usually an inflammation of the thyroid gland. The symptoms of hypothyroidism usually begin slowly, uncharacteristically and insidiously. With increased tiredness, constipation, muscle pain, reduced physical and mental performance and increased feeling of cold, the full picture of a hypofunction is reached. By means of a hormone determination from the blood that is easy to carry out, even mild forms of hypofunction can be determined.

Fortunately, hypothyroidism can be safely treated with thyroid hormone, which is taken in pill form. If this therapy is started immediately, there is no harm to the baby. Correctly dosed thyroid hormone does not lead to any side effects. If a woman who is already being treated for an underactive condition becomes pregnant, a slight increase in the dose may be necessary.

Overactive thyroid gland (hyperthyroidism)

An overactive thyroid can lead to symptoms such as increased sweating, increased heart rate, insomnia, increased bowel movements, nervousness and fatigue. Since some of these symptoms can also be pregnancy-related, making a diagnosis is sometimes difficult. The most common causes of hyperfunction during pregnancy are Graves' disease and chorionic gonadotropin-related hyperthyroidism. While the first form requires immediate drug treatment, the second form is usually less pronounced and almost always heals spontaneously.

In women who are overactive and are planning a pregnancy, long-term treatment for the thyroid disorder should be carried out beforehand. You can choose between thyroid surgery or radioactive iodine therapy. Which of the two forms of therapy is chosen must be decided on a case-by-case basis.

Enlargement of the thyroid gland during pregnancy (goiter)

Diffuse enlargement of the thyroid gland can be a sign of a borderline iodine deficiency, which becomes manifest during pregnancy due to the increased iodine requirement. After a blood sample has been taken to rule out a thyroid dysfunction, the doctor will initiate therapy with iodide tablets or a combination of a thyroid hormone and iodide. If a lump is discovered in the thyroid gland, it must be clarified precisely using ultrasound and usually also with a puncture. This examination is absolutely harmless and hardly painful.

Scintigraphy cannot be performed due to the radiation exposure during pregnancy and breastfeeding.
Most of the nodes are benign. However, a malignant disease of the thyroid gland is rarely suspected. If absolutely necessary, thyroid surgery is most likely to be done in the middle trimester of pregnancy. The operation is usually only performed after delivery.

Postpartum thyroiditis

5-9 percent of all women develop postpartum thyroiditis during the first six months after giving birth. Since the disease usually does not cause pain, it is also known as "silent thyroid inflammation".

Thyroid antibodies are usually elevated. It mainly affects women who have already had elevated thyroid antibodies during pregnancy or who have already had the disease during a previous pregnancy. Typically, there is an overactive condition at the onset of the disease, which lasts a few weeks and then turns into an underactive phase lasting three to nine months. Sometimes this subfunction can persist for longer.

Characteristic symptoms are fatigue, insomnia. Irritability, nervousness, depression. Other diseases can cause the same or similar symptoms. In the case of the corresponding complaints, however, a precise thyroid examination must be carried out in order - if necessary - to be able to initiate treatment.


Changes in the thyroid metabolism already occur during a healthy pregnancy. A sufficient iodine supply for the mother is important for optimal development of the child. In order to be able to diagnose thyroid disorders in the mother in good time, thyroid function and thyroid antibodies should be determined at the beginning of pregnancy, at least in women at risk (already known thyroid disease, family history)

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OA Dr. Wolfgang Buchinger

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