Schwangerschaft und Schilddrüsenüberfunktion
Hyperthyroidism occurs rarely during pregnancy (1%). An existing hyperfunction (hyperthyroidism) often shows spontaneous improvement. It must be kept in mind that a newly developed hyperfunction, if not treated, can lead to complications such as a higher miscarriage rate or premature delivery. A diagnosis of hyperthyroidism during pregnancy by no means constitutes medical grounds for an abortion.
The causes of hyperthyroidism during pregnancy are:
- hCG-induced hyperfunction
- Hyperthyroidism of Graves’ disease (Basedow’s disease)
- Autonomy
Elevated hCG concentration:
In early pregnancy, obviously high B-hCG (concentration of hCG in blood) can occur. The structure of hCG is similar to that of TSH and shows the same affinity for TSH receptors. Thus, in early pregnancy, with elevated hCG, there is an increase in the thyroid hormones. An hCG-induced hyperthyroidism usually has a mild course and often improves spontaneously after the end of the first trimester, even without treatment.
The most common physical complaints with hyperthyroidism are:
- Restlessness
- Rapid heartbeat
- High blood pressure
- Insomnia
- Hypersensitivity to heat
- Muscle weakness
- Frequent bowel movements
- Changes in the skin and nails
- Heavy sweating
Therapy:
1. Iodine and all medication with a high iodine concentration should be avoided.
2. B-hCG induced hyperthyroidism usually has a mild course and shows spontaneous improvement after the first trimester of pregnancy. For this reason, treatment by medication is often not necessary.
3. With Graves’ disease or autonomy and manifest hyperfunction, thyrostatic drugs such as Propylthiouracil (PTU) should be used in the lowest possible doses. The aim of this therapy is to keep fT3 and fT4 in the upper reference range, and TSH in the lower reference range or even below the normal range. These drugs are not teratogenic and cause no malformations, however the fetal thyroid gland is affected by this treatment as well, and there could be a drop in fetal hormone production.
4. A thyroid gland operation during pregnancy should be done only in extraordinary cases such as suspicion of malignant changes, thyrotoxic crisis, and hyperthyroidism that cannot be controlled with medication, or only with very high dosages, as well cases where there are strong side-effects and allergic-toxic reactions to thyrostatics.
Important guidelines:
Please note that toward the end of a pregnancy, there might be an improvement in hyperthyroidism, but that after childbirth, there could be pronounced recurrences of the hyperfunction.
Hyperthyroidism complicates pregnancy. For this reason, patients with known Graves’ disease should definitely undergo treatment before a planned pregnancy.
A combination therapy consisting of a thyroid hormone (Levothyroxine) and thyrostatic drugs should not be used during pregnancy, and the same applies to radioiodine therapy during pregnancy.
Breastfeeding:
During treatment for hyperthyroidism, small amounts of thyrostatic drugs enter breast milk, nevertheless, breastfeeding while taking thyrostatics is safe. Frequent checks on thyroid function are of course required during this period as well.