Prevalence of antithyroid microsomal antibody in thyroid patients of endemic goitre area.

The region of greater Mymensingh known for iodine endemicity, recently came under iodine supplementation as a result of mandatory universal iodination of salt program. Autoimmune thyroid diseases (AITD) are among the most common human autoimmune disorders & presence of autoantibodies to the microsomal antigen (AntiMCAb) is a hallmark of disease activity. Both iodine deficiency & iodine supplementation precipitate increase rate of autoimmunity to the thyroid gland. Study was undertaken to determine prevalence of AntiMCAb positive cases among patients with various thyroid diseases. High resolution ultrasound (HRUS), serum thyroid hormone assays & scintiscan were used to classify the thyroid patients into 8 categories. 221 patients were studied during the stipulated period of 3 months. Male patients were 60 & female patients were 161. Age ranged from 11 to 65 years with median age 29.4 years. AntiMCAb test were done with radioimmunoassay (RIA). 126 patients had antimicrosomal antibody (57.01%). All form of hypothyroid (atrophic, goitrous, Hashimoto's) have very high rate of AntiMCAb positive cases. Highest 89.28% were seen in patients showing feature of Hashimoto's thyroiditis or generalized feature of AITD in HRUS with hypothyroidism, followed had 61.29% positive cases, However, antithyroid antibody was found in all form of thyroid disorders. Nodular goiter had 21.73% antiMCAb positive cases. AntiMCAb found positive at the rate of 33.33% in euthyroid patients with HRUS feature of AITD & diffuse euthyroid goiter, 40% in subclinical hypothyroid, 40% in subclinical hyperthyroid. Female rated higher in range of antimicrosomal antibody positivism. 59% of all thyroid patients among female subjects were AntMCAb positive, where as 51.67% male thyroid patients were positive. Highest number of positive cases found in the 30-35 age group. No definite pattern, however, was observed among age distribution. 20 age matched sample from patients unsuspected of thyroid disease shows 10% AntiMCAb positive compared to 73.33% of the same among same age group of thyroid patients. Frank Hashimoto's thyroiditis with positive antiMCAb and hypothyroidism were all detected by HRUS.