Certain drugs, such as Interferon or Amiodaron, which are used to treat tumors, hepatitis C, or cardiac arrhythmia can cause autoimmune thyroiditis with hyper- or hypofunction.
The standard therapy for treating hepatitis C (CHC).
Autoimmune thyroid disease as a side effect of treatment with Alpha-Interferon (IFN-?) has been reported in an average of 23% of men and 40% of women. Thyroid ailments may occur soon after treatment with Interferon begins, or there can be a delayed onset after treatment has ended. In two-thirds of such cases, the thyroid disease in question was hyperfunction, and in one-third of cases hypofunction. Initial hyperfunction is often followed by hypofunction.
The symptoms are usually mild. The symptoms of the serious forms vary depending on the degree of hyper- or hypofunction. With hyperfunction, symptoms such as restlessness, heart palpitations, hypersensitivity to heat, insomnia, and weight loss occur. With hypofunction, the symptoms include fatigue, listlessness, weight gain, dry skin, and depression.
Thyroid hypofunction is treated with thyroid hormone (levothyroxine) substitution. The aim of this therapy is normalization of the thyroid-hormone balance (euthyreosis) and TSH (roughly 1 µU/l).
For thyroid hypersensitivity, the therapy option depends on the severity of the illness and the patient’s age. With mild forms, a diet low in iodine is sufficient. With more severe forms and younger patients, the thyroid gland should be surgically removed. With severe forms and older patients, radioiodine therapy is the preferred treatment.
This drug, which is effective against cardiac arrhythmia, contains large amounts of iodine. With a daily maintenance dose of 200 mg of Amiodaron, approximately 70 mg of iodide is released. This is equivalent to approximately 300 times the body’s daily requirement. In addition to the iodine content of Amiodaron preparations, the relationship between the chemical structure of Amiodaron and that of thyroid hormones is significant. Consequently, Amiodaron preparations can result in two undesirable phenomena in the thyroid gland:
Amiodaron-induced thyroid hyperfunction, Type I
Lengthy therapy with Amiodaron results in the occurrence or premature development of immune hyperthyroidism if there is a disposition to the condition (Basedow’s disease). The patient complains of the typical symptoms of hyperfunction, such as restlessness, heart palpitations, heavy sweating, hair loss, and weight loss. If possible, the patient will stop taking the drug, and thyroid hyperfunction is treated with high-dose thyrostatic drugs, such as Thiamazol, or there is surgical treatment.
Amiodaron-induced thyroid hyperfunction, Type II
This form of thyroid hyperfunction often occurs in connection with Amiodaron-induced thyroiditis only after Amiodaron has been taken for several months. As a rule, there is then a marginal but abnormally elevated release of thyroid hormones. The patient usually experiences no symptoms. However, this hyperfunction can be followed by hypofunction. Differentiation between the Amiodaron-induced thyroid hyperfunctions Type I and Type II is possible using thyroid gland sonography and thyroid gland scintigraphy. If possible, the patient stops taking Amiodaron. The thyroid inflammation is then treated with steroids such as Prednisolon. With this form of the disease, the effect of thyrostatic drugs is questionable due to the inflammation.
Amiodaron-induced thyroid hypofunction
With an individual disposition to Hashimoto thyroiditis, Amiodaron increases the likelihood of developing that illness. Hypofunction related to Hashimoto thyroiditis is treated with thyroid hormones (levothyroxine).