Prevalence of thyroid autoimmunity in sporadic idiopathic hypoparathyroidism in comparison to type 1 diabetes and premature ovarian failure

Context: Thyroid autoimmunity is the most common coexistent endocrinopathy in type 1 diabetes (T1D), Addison's disease, and premature ovarian failure (POF). Although the role of autoimmunity is being investigated in patients with sporadic idiopathic hypoparathyroidism (SIH), there is little information on coexistent thyroid autoimmunity. Objective: Our objective was 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: We conducted a 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 T-3, free T-4, TSH, and TPOAb (normal <= 34 IU/ml) were measured by electro-chemiluminescence assay. Subjects with 1) serum TSH at least 5 mu U/ml along with TPOAb more than 34 IU/ml; 2) TSH at least 10 mu U/ml but normal TPOAb titers; or 3) 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 those in control and POF groups, but significantly less than in T1D and HT groups. Conclusion: The frequencies of TPOAb and thyroid dysfunction were not significantly higher in patients with SIH than in healthy controls, unlike in patients with T1D and POF.