Side effects of radioiodine therapy
Radioiodine therapy has few side effects. Since the radiation used is emitted by radioactive iodine, which is mainly absorbed by the thyroid gland, the rest of the body is spared. After treatment, a temporarily painful inflammatory reaction of the thyroid gland (radiation thyroiditis) may occur in about one of 20 therapy cycles.
The doctor then prescribes a so-called ice tie and painkillers, which alleviates the symptoms. In rare cases, the inflammatory reaction is contained by short-term treatment with cortisone. Since the radiation is targeted from within during radioiodine therapy, the typical side effects of “normal” radiation from outside, such as hair loss, nausea or diarrhoea, do not occur.
One side effect, which must be accepted in part, is that the body produces no or too little thyroid hormones by destroying the thyroid gland tissue. In order to prevent hypofunction, these must be replaced in such a case by a lifelong intake of thyroid hormone preparations (for example thyroxine). In the case of Graves’ disease or malignant diseases, this is an acceptable consequence of successful radioiodine therapy, as all thyroid tissue must be destroyed in order to achieve a cure.
With thyroid autonomy, on the other hand, it is usually possible to maintain enough healthy areas of the thyroid gland to ensure adequate function. Weight gain is not a direct result of radioiodine therapy. However, the targeted destruction of thyroid tissue can lead to hypothyroidism after therapy.
In the treatment of Graves’ disease and other malignant diseases, this is usually unavoidable, although it is a side effect of thyroid autonomy. In any case, hypothyroidism should be treated by the administration of thyroid hormone preparations, such as thyroxine in tablet form. If this is not done, weight gain may actually occur in addition to many other consequences of the hypofunction.
However, since thyroid function is routinely checked after radioiodine therapy, hypothyroidism is usually detected in time and weight gain can be counteracted by treatment with thyroxine, for example. However, if weight gain does occur, there are probably other causes. In most cases, this is due to a diet that is too high in calories and insufficient physical activity.
Side effects on the eyes are not to be feared by radioiodine therapy. Radiation, which acts specifically on the thyroid gland, spares other organs, such as the eyes. Changes in the eyes or impaired vision must have another cause and should be examined by an ophthalmologist.
Hair loss through radioiodine therapy is not to be expected. Although it is also a form of radiation, it is done from the inside and has a targeted effect on the thyroid gland tissue. Irradiation from the outside of the head area, as in the case of a brain tumor, can lead to hair loss.
Although radiation is released during radioiodine therapy, side effects on the bone marrow are not to be feared. This is because the radioactive iodine acts specifically on the thyroid gland tissue. The side effects feared with other forms of radiation are not to be feared with radioiodine therapy.However, medications that are often used to reduce thyroid function even before radioiodine therapy can, in rare cases, lead to changes in the blood count (e.g. through carbimazole).
This is not a side effect in the bone marrow, but a type of allergic reaction in which the blood‘s defence cells are destroyed. In the long term, any radioactive radiation to which the body is exposed increases the risk of malignant diseases of the bone marrow (blood cancer or leukemia). In addition to the natural radiation in our environment and X-ray examinations, this includes radioiodine therapy.
Nevertheless, it is not a direct trigger for such a serious disease. Even though the radioactive iodine administered during radioiodine therapy is almost exclusively absorbed by the thyroid gland, a small proportion also reaches the salivary glands. This results in less saliva being produced.
However, since this is important, among other things, for dissolving flavor compounds, some people complain of a disturbed sense of taste a few days after the therapy. However, this side effect usually goes away on its own and the taste gradually returns. The disturbed sensation can be prevented by chewing gum and sucking sour candies to stimulate the flow of saliva.
It is also important to drink enough. Side effects on the skin are not to be expected with radioiodine therapy. While with other forms of irradiation, the radioactivity acts on the outside of the body and thus usually affects the skin, there is no such danger with irradiation from the inside through the radioactive iodine. Only the mucous membrane of the stomach may be briefly irritated by the capsule containing the radioactive iodine, which may cause nausea and a feeling of fullness.