CALCITONIN DEFICIENCY IN EARLY STAGES OF CHRONIC AUTOIMMUNE-THYROIDITIS

OBJECTIVES Although calcitonin (Ct) deficiency has been described in c hronic autoimmune thyroiditis (CAT) it is unclear at what stage in the disease it develops. We have analysed the Ct secretory responses of p atients in two different evolutionary stages of CAT, namely the goitro us and atrophic phases. DESIGN We studied the Ct response to combined calcium (2 mg/kg) and pentagastrin (0.5 mu g/kg) intravenous infusion in 27 patients with CAT and 30 normal adult controls. The cases were d ivided into two groups. The first comprised eleven women with CAT and goitrous subclinical hypothyroidism (GH), aged 28.6 +/- 10.1 years-at diagnosis they had increased thyroid autoantibody titres and cytologic al features compatible with stages 1 and 2 of Hashimoto's thyroiditis. The second comprised 16 females with CAT and an atrophic thyroid conf irmed by ultrasound scan, aged 38.0-+9 2 years--these patients were se verely hypothyroid at diagnosis and were termed AH (atrophic hypothyro idism). Both groups (GH and AH) received replacement doses of thyroxin e sufficient to restore euthyroidism for at least six months before th e stimulation tests. Control group (C) consisted of 20 healthy women ( A), aged 30 0 +/- 9 6 years, and 10 healthy men (B), aged 34.7 +/- 8 0 years. Serum Ct was measured by IRMA. The Ct secretory response was r elated to thyroid size and cytological data, when available. RESULTS B asal Ct concentrations in groups GH (0.08ng/l, median) and AH (0.07ng/ l, median) were significantly lower than those of female controls (0.5 8ng/l, median). Stimulated Ct peak values in groups GH (0 08ng/l, medi an) and AH (0.19ng/l, median) were significantly lower than those of f emale controls (13.61 ng/l, median). Also, both basal (2.72 ng/l, medi an) and stimulated Ct levels (35.73 ng/l, median) in male controls wer e significantly higher than in female controls given already. A positi ve correlation between the Ct secretory reserve and thyroid dimensions , evaluated by ultrasound scan, was found only in patients with thyroi d atrophy (AH; rs = 0 61, P< 0.05). CONCLUSIONS We have found low basa l and stimulated calcitonin values in patients with chronic autoimmune thyroiditis and thyroid enlargement, which represents an early phase of chronic autoimmune thyroiditis. Our data have also confirmed previo us findings of deficient calcitonin secretion in advanced stages of ch ronic autoimmune thyroditis in which thyroid atrophy is usually found. These findings may be associated with C-cell destruction following pr ogressive, nonspecific follicular cell damage caused by lymphocytic in filtration and fibrosis of the gland.