[Hyperthyroidism caused by a hormone-producing follicular thyroid cancer].

A well differentiated carcinoma of the thyroid is usually less productive with respect to thyroid hormones than normal thyroid tissue. Very rarely, it happens though that a metastatic follicular carcinoma of the thyroid produces hyperthyroidism as the following example illustrates. In our patient with follicular thyroid carcinoma the radioiodine scan demonstrated an increased uptake of 123I in the right thyroid lobe but also in a lung metastasis, even before thyroidectomy. In contrast, the iodine uptake of the left - normal - thyroid lobe was suppressed. Following thyroidectomy the levels of the thyroid hormones were normal and only dropped into the hypothyroid range after the beginning of the therapy with radioiodine. Hence we conclude that the metastases of a thyroid carcinoma can attain the hormone secretion of a normal thyroid gland and take up more radioiodine than normal thyroid tissue.