Calcitonin reserve in different stages of atrophic autoimmune thyroiditis

The objective of this study was to determine the calcitonin (CT) hormone re serve in different severity of atrophic autoimmune thyroiditis (AAT). Forty -eight female patients with AAT were divided into four groups based on basa l and peak thyrotropin (TSH) values (after oral thyrotropin-releasing hormo ne [TRH], free triiodothyronine (FT3) and free thyroxine (FT4) ranging from normal in group 1 to overt hypothyroidism in group 4. All had thyroid anti bodies. The control group comprised euthyroid females of comparable age, wi thout thyroid antibodies. Basal CT and CT response to calcium infusion (are a under the curve) were investigated as parameters of CT reserve. Basal CT was lower in groups 2 to 4 of patients with AAT (compared to controls), but the difference was not significant. Stimulated CT levels were lower (p < 0 .05) in all groups of patients compared to controls, with markedly reduced CT-secretory reserve in group 4. Thyroid antibody concentrations and, basal and postinfusion calcium levels were not significantly different among the various groups. In conclusion CT deficiency (especially stimulated values) occurs in AAT and is more severe in hypothyroid patients than in earlier s tages of AAT.