Introduction: Hyperthyroidism disorder results from over production of hormones secreted by thyroid gland itself. The present study plan to delineate influence of thyroxin on homocysteine, folate, cyanocobalamine, lipid profile and serum creatinine in hyperthyroid patients before and during treatment with antithyroid drugs. Material and Method: The present study was conducted on 75 pateints of hyperthyroidism of either sex in department of biochemistry, J.L.N. medical college and hospitals, Ajmer. Serum homocysteine, cyanocobalamine, folate level was measured by ELISA while thyroid function test were evaluated by RIA method. Result and discussion: There were significant change in homocysteine, folate, cyanocobalamine, total cholesterol, HDL-cholesterol and LDL-cholesterol in hyperthyroid subjects before and during treatment (P<0.0001) and these emerging evidence suggest that these parameter are influenced by level of thyroxine hormone which were higher in hyperthyroid subjects before treatment with antithyroid drugs. Conclusion: It is concluded that treatment with antithyroid drug reduces the level of thyroxine hormone in hyperthyroid subject increases level of homocysteine and causes dyslipidemia which increases risk of coronary artery disease, angina pectoris in subclinical hyperthyroidism.