Anti-thyroid drugs
What are anti-thyroid drugs?
Anti-thyroid drugs are drugs that are designed to lower the amount of thyroid hormones in the body. This can be done in different ways. Some anti-thyroid drugs inhibit iodine uptake, others inhibit the production of hormones directly.
These drugs are mostly used in the treatment of hyperthyroidism. Another area of application is the immobilization of the thyroid before surgery.
The diagnosis that leads to such an intake is usually made with laboratory tests and an ultrasound examination.
application areas
The most common reason for taking anti-thyroid drugs is an overactive thyroid. This is especially true in younger patients with no or only a small one Goiter a good treatment option. The goal here is to reduce the hormones to a normal level. In some patients, this can even mean that the disease is permanently suppressed.
If the thyroid gland is planned to be operated on for an overactive thyroid gland, anti-thyroid drugs can be taken a few weeks in advance to reduce the risk of the operation. Treatment is usually started four weeks before the planned operation.
Before radioiodine therapy for severe forms of hyperthyroidism, anti-thyroid drugs are also taken as a preparation, as severe crises occur less frequently during treatment. In some sufferers, for whom other treatment approaches are unwanted or not feasible, thyreostatics can also be taken permanently to treat the overactive thyroid. However, this should only be an exception and the dosages should be chosen as low as possible.
In the case of a known hyperthyroidism, anti-thyroid drugs can be used if those affected have to be exposed to large amounts of iodine. This may be necessary for certain imaging procedures with contrast media, since high amounts of iodine can trigger a thyrotoxic crisis.
How do anti-thyroid drugs work?
The anti-thyroid drugs can be divided into two main groups.
The first group are the iodination inhibitors, the so-called Perchlorates. This means that the drugs prevent iodine from being absorbed by the thyroid cells. The thyroid cells need iodine for the production of thyroid hormones. By inhibiting iodine absorption, these anti-thyroid drugs can inhibit the production of T3 and T4 and reduce the levels of hormones in the body.
The second main group of anti-thyroid drugs are the iodization inhibitors.This includes the drugs Thiamazole, Carbimazole and Propylthiouracil. The iodization inhibitors work 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 hormones that are already present are not influenced by the two main classes and therefore the start of the effect is somewhat offset in time.
In addition to the two main groups of anti-thyroid drugs, a high dose of iodine can also temporarily inhibit the release of thyroid hormones. However, this is only suitable for crisis intervention.
Side effects of anti-thyroid drugs
As with all drugs, the side effects can be sorted by frequency. Not all preparations have an identical side effect profile.
With iodination inhibitors, the most common side effect is a slight allergic reaction of the skin, which subsides after a few days.
Occasionally, i.e. in less than one percent of those affected, the following side effects occur:
- Agranulocytoses, i.e. changes in the blood count that must be treated immediately,
- Taste disorders,
- Drug fever and
- Water retention.
Very rarely does it happen:
- other changes in the blood count, such as thrombocytopenia or pancytopenia,
- the insulin autoimmune syndrome,
- Polyneuropathies,
- Vascular inflammation,
- Liver inflammation,
- drug-induced lupus,
- Kidney infections and
- Joint inflammation.
With the iodination inhibitors, the more common side effects are nausea and vomiting. The drug fever occurs here a little more frequently than with the iodization inhibitors.
Occurring side effects should always be discussed with the attending physician so that a dose adjustment or a change of medication can take place.
Weight gain
The main indication for the use of anti-thyroid drugs is hyperthyroidism. With an overactive thyroid, those affected have an increased metabolic performance and an increased need for calories. Taking the anti-thyroid drugs should normalize the metabolism. However, since those affected have adapted their diet to the greater need, weight gain initially occurs. However, this can be limited again by normalizing the daily calorie intake.
Interactions
Anti-thyroid drugs have relatively few direct interactions with other drugs, as these act very specifically on the thyroid gland. Increased or decreased amounts of iodine can have an influence on the effect of the anti-thyroid drugs and thus other drugs containing iodine can also have an effect on it.
Secondly, the effect of other drugs can be increased, since the thyreostatics downregulate the metabolism and the drugs can be broken down more slowly. In this case a dose adjustment of the other drugs is necessary.
Interaction with the pill
Thyreostatics are very specific drugs that affect the iodine balance and the incorporation of iodine. This does not affect the metabolism of the birth control pill.
However, as some anti-thyroid drugs can cause nausea and vomiting, women affected should use additional contraception while side effects occur.
Anti-thyroid drugs and alcohol
The anti-thyroid drugs have relatively few interactions with other substances, as they have a very specific effect on thyroid hormone production and iodine is only required there. Therefore, there are no direct interactions with alcohol either.
Overall, however, thyrostatic drugs can downregulate the metabolism and thus also ensure that alcohol and other toxic substances are broken down more slowly than usual. The effect can therefore increase.
Contraindications
In the event of hypersensitivity to the active ingredients themselves or to other components of the medication, they must not be taken any further, as otherwise a life-threatening allergic shock can be triggered.
Changes in the blood count are also a reason for exclusion from treatment with anti-thyroid drugs.
In the case of a known biliary tract disease, anti-thyroid drugs are contraindicated.
In the case of a goiter that has already grown into the chest, anti-thyroid drugs should not be taken, as the drop in hormone concentration can stimulate the thyroid to grow and this can then constrict other body structures.
pregnancy and breast feeding period
The intake of anti-thyroid drugs must be carefully considered during pregnancy.
If left untreated, an overactive thyroid increases the risk of malformations and premature births, but thyreostatics can also enter the child's body via the placental barrier and lead to thyroid disease and growth retardation.
Thyreostatics should be avoided during breastfeeding, as they can get into breast milk and cause hypothyroidism in the child. Here either the child should be weaned or the mother should pause the medication.
Dosage of anti-thyroid drugs
The exact dosage of the anti-thyroid drugs depends on the exact preparation and many individual factors.
At the start of therapy, a dose is chosen that completely blocks hormone synthesis. A maintenance dose is then given later, which for carbimazole is between 5 and 20 mg. This only partially blocks production. The most important laboratory value, which is used for the dosage, is the TSH - a hormone that regulates the production of thyroid hormones.
The dosage often has to be adjusted further in the course of therapy.
What do anti-thyroid drugs cost?
Thyroid drugs are a necessary therapy for a disease and the drugs are therefore covered by the statutory health insurance companies. Those with statutory health insurance only have to pay an additional five euros.
A pack of carbimazole with 100 tablets, each with 10 mg of active ingredient, costs around 20 euros. However, the costs vary greatly depending on the dosage and manufacturer.
Alternatives to anti-thyroid drugs
Anti-thyroid drugs are only one option in the treatment of hyperthyroidism. However, the effect of the anti-thyroid drugs is not sufficient, especially if the hyperfunction is more pronounced.
An operation in which part or all of the thyroid tissue is removed can permanently eliminate the disease, but those affected must take thyroid hormones for life.
Even with radioiodine therapy, the thyroid tissue is completely destroyed and the overproduction of hormones is stopped. This is a therapy with radioactive iodine.
The person affected and the doctor treating them should discuss the appropriate therapy together.
Read our article about this: The therapy of hyperthyroidism.
Are there over-the-counter anti-thyroid drugs?
The classic thyreostatics all require a prescription. The use of anti-thyroid drugs is a serious intervention in the body functions and self-therapy could have serious consequences.
With a slight overactive thyroid gland, natural preparations such as wolfwort can be used. These over-the-counter remedies have a slight inhibitory effect on hormone production, but are not suitable for treating a fully developed hyperthyroidism.
