The effect of folic acid and levothyroxine combination therapy on serum homocysteine levels of hypothyroid patients

Elevated level of serum homocysteine, as an independent risk factor for cardiovascular diseases, has been reported in hypothyroid patients. Considering the effect of levothyroxine on lowering homocysteine levels in these patients, and the fundamental role of folate in the metabolic cycle of homocysteine, this study was performed to compare the level of homocysteine in patients with hypothyroidism following treatment either with levothyroxine alone or in combination with folic acid. In this double-blind clinical trial study, 60 hypothyroid patients were randomly divided into two groups (n=30 each), and both were treated with 50-100 ‌µg of levothyroxine, with conjunction of an additional 1 mg folic acid (cases) or placebo (controls). The level of fasting homocysteine, folic acid, and vitamin B12 was measured and compared in all participants at the beginning of the study and after TSH levels were normalized. The level of homocysteine in the case group was decreased from 15.77±6.33 µmol/L to 10.8±3.54 µmol/L (p<0.001), and was also decreased in the control group from 15.69±6.4 µmol/L to 13.9±6 µmol/L (p=0.03). The difference in the mean serum homocysteine level between 2 groups was statistically significant at the end of the study (p=0.0165). Although the level of homocysteine was decreased in both groups, it was lowered to a greater extent in the group who received levothyroxine and folic acid. It seems that using folic acid in conjunction with levothyroxine can lower the potential harmful effects of homocysteine, which may even be exerted over a short-time period more efficiently.