Clinical utility of serum holotranscobalamin in the assessment of Vitamin B12 deficiency in patients with Hypothyroidism

Thyroid disorder is the second most frequently encountered endocrinological condition after diabetes mellitus. When vitamin B12 deficiency coexists with hypothyroidism, neurological symptoms and signs are more pronounced. Holotranscobalamin (Active B12) may be a more sensitive marker in the early diagnosis of Vitamin B12 deficiency than total B12. The study aimed to evaluate the serum levels of active B12 in patients with clinical hypothyroidism and to correlate active B12 and thyroid profiles. The case-control study was carried out in a tertiary hospital on 80 study subjects, comprising of 40 confirmed hypothyroidism patients and 40 age- and gender-matched healthy controls. Serum thyroid profile and active B12 assays were performed by Chemiluminescent Microparticle Immunoassay. Statistical methods such as independent t-test and Pearson's correlation were used to compare and correlate quantitative data. A significant percentage (90%) of hypothyroid patients had vitamin B12 deficiency, with a mean value of 17.39 ± 5.73 pmol/L. Active B12 showed a positive correlation with T3 (r = 0.818; P < 0.001) and T4 (r = 0.851; P < 0.001) and a negative correlation with TSH (r = -0.930; P < 0.001). Vitamin B12 deficiency was found in patients with hypothyroidism. This vitamin B12 deficiency may be caused by inadequate malabsorption, as seen in hypothyroidism. HoloTC (Active B12) may be a promising marker for early detection and management of B12 deficiency, which may be beneficial in preventing irreversible neurological damage at an early stage.