[Chronic autoimmune thyroiditis and C-cell hyperplasia. Study of calcitonin secretion in 24 patients].

Serum calcitonin (CT) was determined by radioimmunoassay, using two monoclonal antisera, in 22 women and two men, who had Hashimoto's thyroiditis as confirmed by echographic, immunological or cytological criteria; in 23 patients, serum CT levels were measured after intravenous infusion of pentagastrin (Pg). In 21 cases, basal and Pg stimulated serum CT concentrations were normal. A 61-year-old woman and a 63-year-old man, both euthyroid, had high serum basal CT: 12 pg/ml and 35 pg/ml; infusion of Pg resulted in abnormal increases in serum CT levels: respectively 64 pg/ml and 115 pg/ml. Another patient, a 65-year-old woman with primary hypothyroidism had high serum basal CT: 90 pg/ml (the Pg stimulation test was not done because of ischemic heart disease). Each of these 3 patients had a total thyroidectomy. Pathological examination of the thyroid showed typical features of Hashimoto's thyroiditis and extensive C-cell hyperplasia. After surgery, serum CT levels fell to normal. Therefore, a high serum CT can be observed as the consequence of C-cell hyperplasia in Hashimoto's thyroiditis.