RESUMEN
Objective: To assess the natural history and progression of subclinical hypothyroidism and tostudy factors which help predict evolution of subclinical hypothyroidism into overthypothyroidism. Methods: Longitudinal study in 40 children (2-16 yrs) presenting withsubclinical hypothyroidism in a tertiary care unit in Chennai, India. Patients showing evidenceof overt hypothyroidism or thyroid stimulating hormone ?15 mIU/mL during follow-up werestarted on thyroxine. Others were followed up with 3-monthly thyroid function tests up to oneyear. Results: At the end of our study period 3 (7.5%) were overtly hypothyroid, 16 (40%)remained as subclinical hypothyroid, and 21 (52.5%) became euthyroid. Evidence of autoimmunity at baseline was a significant (P<0.05) risk factor for progression to overthypothyroidism. Conclusions: Subclinical hypothyroidism in children, with thyroidstimulating hormone upto 15 mIU/L and irrespective of thyroid autoimmunity, needs onlyperiodic clinical and biochemical follow up. Thyroid autoimmunity may point to an increasedprobability of progression to overt hypothyroidism.