An association between acromegaly and thyroid carcinoma.

Acromegaly has been associated with goiter as well as with benign and malignant tumors. Three cases of thyroid carcinoma in patients with acromegaly had been reported in the literature. We previously reported two additional cases of thyroid carcinoma and now present a third from 100 patients with acromegaly, exceeding the expected prevalence. All three thyroid carcinomas were multifocal, suggesting a generalized promotion toward malignancy. These patients had elevated levels of growth hormone and somatomedin-C [insulin-like growth factor (IGF-1)] at the time of thyroid carcinoma diagnosis. We discuss the role of IGF-1 in both benign and malignant thyroid growth, including the presence of IGF-1 receptors on thyroid cells, stimulation of thyroid cell replication by IGF-1, and paracrine secretion of IGF-1 and its binding proteins by thyroid cells. We propose possible mechanisms for the development of thyroid carcinoma in patients with acromegaly and discuss implications for the physician treating patients with acromegaly.