Thyroid cancer in suppressed contralateral lobe of patients with hot thyroid nodule.

We studied 60 patients with thyrotoxicosis due to single toxic nodule. At surgery in 3 patients (5%) a papillary carcinoma has been detected in the contralateral suppressed lobe. Thyroid function tests and thyroid scan confirmed thyrotoxicosis. Thyroid stimulating hormone (TSH) was undetectable in all patients. It is common opinion that differentiated thyroid tumour growth is TSH dependent. On the basis of our study two hypotheses are possible: (1) the development of thyroid carcinoma precedes the adenoma and suppressed TSH levels inhibit tumour growth; (2) suppressed TSH levels do not protect patients from the occurrence of cancer. In the evaluation of hot thyroid nodule we suggest careful ultrasonographic control in order to look for nodules outside the adenoma. A complete surgical examination of the whole thyroid gland is required and intraoperative biopsies are advocated in abnormal areas.