Therapy of benign thyroid diseases

Thyroid hormones are essential for the human organism. Among other things, they influence the energy metabolism, the gastrointestinal tract, the cardiovascular system and the mental state. Both too little (hypothyroidism) and too much thyroid hormone (hyperthyroidism) can lead to serious disorders of various bodily functions.

Hyperthyroidism is a relatively common disease in Germany. The most common causes of this are so-called thyroid autonomy or an immune disorder known as Graves' disease

Drug therapy can only alleviate the symptoms of this disease, but cannot usually eliminate the cause permanently. This can only be achieved with radioiodine therapy or the surgical removal of the affected parts of the thyroid gland. Both treatment methods can be classified as equivalent in terms of therapeutic success. Which treatment option is most suitable in each individual case is decided together with the patient in an interdisciplinary discussion.

Radioiodine therapy has been recognized as an effective and side-effect-free treatment method for more than 50 years. It is used to specifically treat overactive areas of the thyroid gland while sparing normally functioning parts. A radioactive isotope (iodine 131) of normal iodine, which you know as an important component of food, is used.

Indications

• The indications for radioiodine therapy are
• functional autonomy
• immunogenic hyperthyroidism
• goitre reduction therapy for endemic goitre
• Subclinical hyperthyroidism (compensated thyroid autonomy) with cardiac risk or before planned contrast medium applications

Contraindication: An absolute contraindication for radioiodine therapy is pregnancy and suspected malignancy. A thyroid carcinoma must first be reliably ruled out.

Therapy of thyroid carcinoma

Tracheal constriction or tracheomalacia are regarded as relative contraindications; in this case, surgical repair of the thyroid gland has priority. A younger age of the patient is no longer considered a contraindication for radioiodine therapy.

Principle and implementation

The principle of radioiodine therapy is based on the application of a sufficient dose of radiation, based on experience, to eliminate the diseased thyroid tissue. This dose is achieved by administering an activity level of iodine-131 calculated individually for each patient. In addition to the desired target dose, the required amount of activity depends on the mass of the thyroid gland, the retention time (half-life) and the percentage uptake of the radioactive iodine into the thyroid gland. The mass of the thyroid gland is determined sonographically, the half-life and uptake by means of the so-called radioiodine test after administration of a small amount of test activity. Radioiodine testing prior to radioiodine therapy is performed on an outpatient basis. If clinically indicated, this can also be carried out as an inpatient if necessary.

Dose concepts

The aim of radioiodine therapy is to eliminate hyperthyroidism, with the aim of achieving normal thyroid function in the case of autonomies. This is achieved in approx. 90 % of cases. In immunogenic hyperthyroidism (Graves' disease), the so-called ablative concept has become established, i.e. the aim is to achieve extensive functional elimination of the thyroid gland. This approach is based on the experience that the long-term results with regard to the recurrence rate, the further development of thyroid autoantibodies and eye symptoms are significantly better than with a dose concept that aims for normal thyroid function.

Implementation of radioiodine therapy

In accordance with legal requirements, radioiodine therapy in Germany can only be carried out on an inpatient basis.

In the treatment of thyroid autonomy, hyperthyroidism must be present; in this situation, it is ensured that the healthy thyroid tissue does not absorb radioactive iodine and is therefore largely spared. In some cases, this condition must be achieved by administering thyroid hormone tablets; if necessary, your family doctor will inform you about this. As a rule, medication to treat hyperthyroidism (thyreostatics, e.g. carbimazole or Favistan) should be avoided for approx. 10 days before radioiodine therapy, but this will be decided on a case-by-case basis depending on the thyroid hormone situation. In any case, you should ensure that your diet is low in iodine (e.g. avoid sea fish, mussels etc.). You should also take particular care not to use any medication containing iodine (X-ray contrast media, vitamin preparations, eye drops, disinfectants).

After you have received your individually determined therapeutic amount of iodine-131, you must remain in your hospital room for approx. 48 hours, after which you can use the ward's own terrace or the recreation room with fitness facilities.

During treatment, your thyroid and whole-body activity will be measured daily; the measurement results will provide information about the actual therapy dose achieved and your expected day of discharge. If a significant underdosage is foreseeable, follow-up therapy can be considered during the inpatient stay.

Side effects and risks

In rare cases, patients who have to be treated with high activity levels due to relatively large strands may experience a type of inflammatory reaction (radiation thyroiditis) in the first few days after administration of radioiodine, which can usually be treated without problems using symptomatic measures (e.g. ice tie) and non-steroidal anti-inflammatory drugs. Corticosteroids are only required in very rare cases.

In order to avoid a heavy load on the salivary glands - the radioactive iodine is partially absorbed into the salivary gland - a good flow of saliva must be ensured, e.g. by giving lemon juice or sour sweets.

In patients with Graves' disease and a pre-existing endocrine orbitopathy, radioiodine therapy is carried out under corticosteroid protection. This prevents a therapy-related worsening of the endocrine orbitopathy.

Extensive studies from the USA and Sweden show that there is no relevant increased risk of thyroid cancer or malignancies of other organs in adults after radioiodine therapy that can be attributed to the radiation treatment, and an increased risk of genetic abnormalities can also be denied.

Results of radioiodine therapy

The aim of radioiodine therapy in thyroid autonomy is to eliminate hyperthyroidism, which is achieved in more than 90% of patients; the rate of necessary repeat therapies is around 5%. Over time, hypothyroidism can develop in around 10% of patients, which may need to be compensated for with the administration of thyroid hormones.

In Graves' disease, the so-called ablative approach is generally used. In over 90% of cases, the hyperthyroidism is successfully eliminated with the aim of achieving hypothyroidism, which is then substituted with thyroid hormone.

Radioiodine therapy can also be used to reduce the goitre or nodule volume by 30-50%.

Aftercare

On the day of discharge, you will be given a recommendation regarding any necessary radiation protection measures. You will also receive a short letter informing your family doctor about the radioiodine therapy and any necessary thyroid medication.

Your thyroid hormone levels should be measured for the first time approximately 3-6 weeks after the treatment.

Approximately 6 months after radioiodine therapy, a detailed examination should be carried out to monitor the success and document the results of the therapy. In addition to the determination of thyroid laboratory values, this examination includes sonography and scintigraphy.

Patients with hyperthyroidism, regardless of the cause and type of treatment (medication, surgery, radioiodine therapy), must have their thyroid function monitored throughout their lives in order to detect recurrences of hyperthyroidism or the occurrence of (late) hypothyroidism at an early stage. In the long term, monitoring intervals of 1-2 years are also recommended for euthyroid function.

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