Thyrostatics

What are thyrostatics?

Thyrostatics are drugs that are supposed to lower the amount of thyroid hormones present in the body. This can be achieved in different ways. Some thyrostatics inhibit the absorption of iodine, others directly inhibit the production of the hormones.

These drugs are mostly used in the treatment of hyperthyroidism. Another area of application is the immobilization of the thyroid gland before surgery. The diagnosis leading to such an intake is usually made with laboratory values and an ultrasound examination.

Fields of application

The most common reason for taking thyrostatic drugs is hyperthyroidism. This is a good treatment option especially for younger patients with no or only a small goiter. The aim here is to reduce the hormones to a normal level.

In some patients, this can even mean a permanent suppression of the disease. In the case of a planned operation on the thyroid gland in the case of hyperthyroidism, thyrostatic drugs can be taken a few weeks in advance to reduce the risk of the operation. The treatment is usually started four weeks before the planned operation.

Before radioiodine therapy for severe forms of hyperthyroidism, thyrostatics are also taken as a preparation, as severe crises during treatment are less frequent. In some patients, for whom other treatment approaches are unwanted or not feasible, thyrostatic drugs can also be taken permanently to treat hyperthyroidism. However, this should only be the exception and dosages should be kept as low as possible. In the case of a known hyperthyroidism, thyrostatics can be used if the affected person has to be exposed to large amounts of iodine. This may be necessary in certain imaging procedures with contrast medium, as high iodine quantities can trigger a thyrotoxic crisis.

How do thyrostatics work?

Thyrostatics can be divided into two main groups. The first group are the iodination inhibitors, the so-called perchlorates. This means that the drugs prevent the absorption of iodine into the thyroid cells.

The thyroid cells need the iodine for the production of thyroid hormones. By inhibiting the uptake of iodine, these thyrostatic drugs can inhibit the production of T3 and T4 and reduce the amount of hormone in the body. The second main group of thyrostatic drugs are the iodization inhibitors.

These include the drugs thiamazole, carbimazole and propylthiouracil. The effect of the iodization inhibitors takes place in the thyroid cells. The active ingredient prevents iodine from being incorporated into the amino acid tyrosine and thus fewer thyroid hormones are produced.

The existing hormones are not affected by the two main classes and therefore the onset of action is somewhat delayed. In addition to the two main groups of thyrostatic drugs, a high dose of iodine can also inhibit the release of thyroid hormones for a short period of time. However, this is only suitable for crisis intervention.