Differential diagnosis of hyperthyroidism

There are probably two reasons for hyperthyroidism: 1. A disturbance in the immune system. This leads to the production of autoantibodies which predominantly stimulate thyroid function. 2. An increased formation of autonomus follicles in the thyroid gland during the development of a goiter. Autonomus follicies can be located within the thyroid gland in a focal or disseminated pattern. They are found predominantly in bigger, long-standing goiters with degenerative areas. The extent of autonomy is probably determined by the amount to autonomous follicles and their activity. In the euthyroid state autonomy can be detected by a subnormal TRH test. Quantitative scintigraphy under suppression is probably more sensitive. In goiters with autonomy, transition from the euthyroid into the hyperthyroid state especially in areas of iodine deficiency is often induced by application of iodine containing drugs and X-ray media. It the patient is already in a hyperthyroid state its immunogenic and non-immunogenic origin can be recognized with rather high probability by certain clinical symptoms and by some simple laboratory investigations. This may have significance for the selection of therapy. (orig.)