Novel evidence of relationship between serum vitamin B12 and folate with total vitamin D in subclinical hypothyroidism

Introduction and Aim: Subclinical hypothyroidism is an early form of thyroid dysfunction, which may develop into full-blown hypothyroidism in absence of proper dietary and medical intervention. Subclinical hypothyroidism (SCH) can induce metabolic derangements and increase risk of hypertension and cardiovascular disease. Hyperhomocysteinemia, a risk factor of CVD, is the most prevalent metabolic derangement in subclinical hypothyroidism. Thyroxine and vitamin D modulate the expression of genes and regulate the activity of methyl transferase needed for conversion of homocysteine to methionine, which requires folate and cobalamin as  cofactors. The aim of the study is to establish the interrelationship between the three vitamins in SCH. Materials and Methods: Study population included 100 freshly diagnosed subclinical hypothyroid patients and 50 age and sex matched euthyroid adults. Serum TSH, T3, T4, total vitamin D, vitamin B12 and folate were estimated by electrochemiluminescence Immunoassay (ECLIA) using Cobas 6000 autoanalyzer. Results: Serum TSH was significantly high in SCH patients compared to euthyroid subjects. Serum total vitamin D, vitamin B12 and folate decreased significantly in SCH patients compared to the controls with p values being 0.001, 0.05 and 0.01 respectively. There was a significant negative correlation between vitamin D and TSH (r = - 0.38 p=0.03). Further, correlation between vitamin D with cobalamin (r=0.46, p=0.009) and with folate (r=0.42, p=0.01) were also statistically significant. Conclusion: Based on the findings, it is imperative to link vitamin deficiencies with thyroid dysfunction and vitamin supplementation in SCH patients may prevent the progression to hypothyroidism.   Keywords: Subclinical hypothyroidism; cobalamin; folate; vitamin D; TSH.