10.22376/ijpbs.2019.10.1.p1-12 Volume 6 Issue 2 2015 (April - June) Iron deficiency is one of the overlooked cause of thyroid dysfunction. This study was done to find out the effect of ferritin deficiency on thyroid hormonal activity. 186 subjects included in this study were divided into two groups, those with S. ferritin lessThan 20ng/mL as cases (n=91) and greaterThan 20ng/ml (n=95) as controls. Thyroid stimulating hormone was also measured in all subjects. Values were expressed as mean ± SD. Unpaired't' test & Pearson's correlation test performed to see the level of significance. P value lessThan 0.05 taken as significant. Ferritin levels in cases and controls were 10.54±5.5 and 153.2±106.7 ng/mL respectively (p lessThan 0.0001). TSH levels in cases and controls were 5.23±3.5 and 3.27±2.25 µIU/mL respectively (p lessThan 0.0001).Serum. Ferritin & Serum.TSH showed negative correlation in controls and cases which was not statistically significant. Significant difference in thyroid hormone status in iron deficient people could be a reflection of disturbed activities of iron dependent enzyme, thyroid peroxidase. Iron deficiency lowers TPO activity. This will decrease circulating thyroid hormone concentrations and increase TSH levels. T.V.K. PADMAJA, PRISCILLA ABRAHAM CHANDRAN AND K.S.S.SAIBABA Iron deficiency, Serum Ferritin, Thyroid stimulating hormone, Thyroid peroxidase. 103-107