THYROID HORMONE-PRODUCING METASTASES IN DIFFERENTIATED THYROID-CANCER

Thyroid hormone production by metastases of differentiated thyroid car cinoma is very rare and its pathogenesis is still unknown. The aim of this study was to present some clinical and demographic evidence that thyroid hormone-producing metastases of differentiated thyroid carcino ma are related to environmental factors, probably iodine deficiency. A cross-sectional study was performed on thirty-five patients with dist ant metastases, identified in a group of 125 patients with differentia ted thyroid carcinoma previously submitted to total or near total thyr oidectomy. In 6 patients (5 females, 1 male; age range, 50 to 64 yr) w e had evidence that the metastases were actively producing thyroid hor mones and in 29 patients (21 females, 8 males; age range 8 to 84 yr) t he metastases were considered to be nonthyroid hormone-producing. Seru m levels of T3, T4, and thyroglobulin were measured by RIA, TSH by IRM A, and I-131 whole-body scintigraphy was performed 72 h after 187 Mbq of I-131. All patients with metastases producing thyroid hormones pres ented a pure follicular thyroid carcinoma. They also differed from pat ients with nonproducing metastases in the frequent presence of goiter of long duration as the first clinical manifestation of thyroid diseas e (p<0.01), and a higher proportion of patients coming from an iodine deficient area (5/6 vs. 6/29, p<0.05). In these patients the serum thy roglobulin levels tended to be higher (p=0.069) as compared with the n onproducing metastases group. In conclusion, a late diagnosis of folli cular carcinoma in patients with longstanding multinodular goiter allo wed the development of well differentiated and bulky metastases retain ing the ability to produce thyroid hormones.