Therapy of benign thyroid diseases

Thyroid hormones are indispensable for the human organism. They affect the energy metabolism, the intestinal tract, the cardio-vascular system, and the mental state. Both too little (hypothyroidism) and too much (hyperthyroidism) of thyroid hormones may seriously disturb various body functions. Hyperthyroidism is a relatively frequent disease in Germany. The most frequent reasons are so-called thyroidal autonomy, or an immunological disease, so-called Grave's disease (Morbus Basedow). Medication can only mitigate this disease’s symptoms, but generally not permanently remove the cause. This is only possible with the so-called radio iodine therapy or surgical removal of the thyroid tissue. Both treatments have an equivalent success rate. In an interdisciplinary discussion, we decide on an individually with the patient which therapy option is best suitable.

Radio iodine therapy has been accepted as an effective treatment without severe side effects for more than 50 years. It selectively treats hyperactive thyroid areas; normally functioning thyroid tissue will not be affected. A radioactive isotope (I-131) of iodine, known as an important nutrition component, will be used.

Indications

• Indications of radio-iodine therapy are
• functional autonomy
• immunogenic hyperthyroidism (M. Basedow, Grave's disease)
• struma reduction therapy for endemic struma
• sub-clinical hyperthyroidism (compensated thyroid autonomy) in case of cardiac risk factors or prior to planned application of contrast agents.

Contraindications: One absolute contraindication for radio-iodine therapy is pregnancy and suspicion of malignant tumors, especially thyroid cancer before operative removal.
Relative contraindications are a narrowed trachea or tracheomalacia; here, thyroid surgery is the primary therapy option. Patient’s young age is no longer considered a contraindication for radio-iodine therapy anymore.

Principle and implementation

The principle of radio iodine therapy is based on the application of a sufficient dose of radiation, based on empirical data, to inactivate the diseased thyroid tissue. This dose will be achieved by administration of I-131, specifically calculated for each patient. The required dose is, in addition to the targeted dose, dependent on the thyroid mass, the duration (half-life period) and percentage uptake of radio-active iodine in the thyroid (uptake). The thyroid mass will be calculated by sonography; half-life and uptake will be determined by the so-called radio iodine test after administration of a small amount of test doses of I-131. The radio iodine test may be done as an in-patient or out-patient treatment, depending on your personal requirements and circumstances.

Dose concepts

Radio iodine therapy aims for the removal of hyperthyroidism. In case of autonomies, a regular thyroid function is the primary aim. However depending on the amount of remnant unaffected thyroid tissue hypothyroidism may be unavoidable. Removal of hyperthyroidism is achieved in approx. 90% of all cases. For immunogenic hyperthyroidism (Grave's disease), the so-called ablative concept is preferred, where the thyroid will be functionally eliminated. This process is based on the experience that the long-term results regarding recurrence, further development of thyroid auto-antibodies and regarding eye symptoms are substantially better than for other dose concepts.

Implementation of radio iodine therapy

Complying with legal requirements, radio-iodine therapy may only be done in Germany as an in-patient treatment.

The prerequisite of an optimal treatment of focal thyroid autonomy is a suppression of TSH (usually due to hyperthyroidism); in this situation, the healthy thyroid tissue will not take up radio-active iodine and is therefore mostly spared by radiation. In individual cases, this state has to be achieved by administration of thyroid hormones. If needed, your GP will inform you. Generally, drugs for treating the hyperfunction (thyreostatics, e.g. Carbimazol or Favistan) will have to be renounced approx. 10 days prior to the radio-iodine therapy; however, this is decided individually, depending on the thyroid hormone situation. In any case, you should avoid food with high iodine content (e.g. do not eat sea fish, mussels etc.). You should in particular avoid iodine-containg drugs (contrast agents, vitamin supplements, eye drops, disinfectants).
Having received your individually determined therapeutic dose of I-131, you will have to stay in the patient room for approx. 48 h; afterwards you may use the unit’s terrace or the lounge.
During the treatment, residual thyroid and body radioactivity will be measured daily; the measured results are used to determine the achieved therapy dose and your expected discharge day. In case of expected under-dosing, a follow-up therapy is possible already during the in-patient stay.

Side effects and risks

Patients who, for a relatively large goiter, have to be treated with high activity amounts may experience a kind of inflammatory reaction (radiation thyroiditis) during the first days after radio-iodine administration, which can generally be addressed without problems by treating the symptoms (e.g. ice necktie) and non-steroidal antiphlogists. Corticosteroids are rarely necessary.
To prevent an unnecessary radiation of the salivary gland – the radioactive iodine is partially taken up into the salivary gland -, good salivation must be ensured; this is for instance done by drinking lemon juice or eating sour drops.

Patients with Grave's disease (M. Basedow) and a history of endocrine orbitopathy will receive radio-iodine therapy under cortiscosteroid protection. With this a therapy-related deterioration of the endocrine orbitopathy is prevented. Studies on large patient cohorts from the U.S. and Sweden show that adults do not have a radio-therapy related increased risk neither for thyroid cancer nor for malignant tumors in other organs after radio-iodine therapy; likewise, a higher risk for genetic anomalies in children born after a radio iodine therapiy does not exist.

Results of radio-iodine therapy

The main aim of radio-iodine therapy for thyroid autonomy is removal of hyperthyroidism; this is successful for more than 90% of all patients. The approx. 5% of the cases a second therapy is necessary. Over time, hypothyroidism is seen in approx. 10% of all patients which can be compensated by external administration of thyroid hormones.

Grave's disease (Morbus Basedow) is generally treated with a so-called ablative concept. Here, more than 90% of all treatments result in a removal of hyperthyroidism, targeting hypothyroidism with followed substitution of thyroid hormones.

Furthermore radio-iodine therapy reduces thyroid or node volume by 30-50%.

Patient follow-up

On the day of discharge you will get a letter for your GP summing up the therapy and the necessary follow up and you will be given a recommendation regarding possibly required precautions for radiation protection. Approx. 3-6 weeks afterwards, a first determination of the thyroid hormones should be done. Approximately 6 months after the radio-iodine therapy, a detailed test documenting therapy results should be performed. In addition to determination of the laboratory thyroid values, this includes sonography and scintigraphy. Patients with hyperthyroidism will need a life long control of thyroid function in order to discover recurrence of hyperthyroidism or occurrence of (late) hypothyroidism; this is necessary independently of the primary form of treatment (radio-iodine therapy or surgery). On the long term, control intervals of 1 to 2 years are recommended.