Context: Thyroid autoimmunity is the most common coexistent endocrinopathy in type1 diabetes (T1D), Addison's disease and premature ovarian failure (POF). Although role of autoimmunity is being investigated in patients with sporadic idiopathic hypoparathyroidism (SIH), there is little information on coexistent thyroid autoimmunity.

Objective: To assess the prevalence of thyroid peroxidase autoantibodies (TPOAb) and thyroid dysfunction in patients with SIH and its comparison with that in T1D, POF and Hashimoto's thyroiditis (HT) and age and sex matched healthy controls (for SIH).

Design and setting: Case control study in a tertiary care setting.

Patients and Methods: Subjects were consecutive patients with SIH (n = 87), T1D (n = 100), POF (n = 58) and HT (n = 47) and healthy controls (100 females and 64 males). Serum free T3, free T4, TSH and TPOAb (normal 34 IU/ml) were measured by electrochemiluminiscence assay. Subjects with, a) serum TSH 5µU/mL along with TPOAb > 34 IU/mL or b) TSH 10 µU/mL but normal TPOAb titers or c) Graves' disease were considered to have thyroid dysfunction.

Results: TPOAb positivity (> 34 IU/ml) in females was 14.6% in SIH, 24.1% in POF and 42.1% in T1D compared with 76.6% in HT and 9% in healthy controls. The frequencies of TPOAb positivity and thyroid dysfunction in patients with SIH were comparable to that in controls and POF group, but significantly less than that in T1D and HT groups.

Conclusion: The frequencies of TPOAb and thyroid dysfunction were not significantly higher in patients with SIH than that in healthy controls, unlike in patients with T1D and POF.