Nearly 30% of patients with hypothyroidism have deficiency of vitamin B12 compared to healthy adults, suggests a study published in the journal Frontiers in Endocrinology.¹

Researchers from Peru carried out a systematic review and meta-analysis to measure the serum levels of vitamin B12 among patients with thyroid disorders and compared them with those who do not have any thyroid disorder. They also looked for the anti-parietal cell antibodies (APCA) in patients with thyroid disorders. A total of 64 studies published between 1967 and 2022, involving 28,597 patients were included for the analysis following a search of Scopus, Web of Science, Embase and PubMed databases. Out of the 64 studies, 17 were related to B12 levels in patients with hyperthyroidism, 40 ascertained B12 levels in patients with hypothyroidism, 21 estimated B12 levels in autoimmune thyroid disease, while the remaining 10 examined B12 levels in patients with subclinical hypothyroidism.

Compared to the healthy subjects, hypothyroid patients had lower B12 levels with a mean difference of -60.67 pg/mL. The B12 levels were comparable between patients with hyperthyroidism, autoimmune thyroid disease or subclinical hypothyroidism. Twenty-seven percent of patients with hypothyroidism had B12 deficiency. A similar percentage (27%) of those with subclinical hypothyroidism were B12 deficient. Among patients with hyperthyroidism and autoimmune thyroid disease, B12 deficiency occurred in 6% and 18%, respectively. Anti-parietal cell antibodies were detected in nearly 30% of patients with autoimmune thyroid disease.

This study confirms that patients with hypothyroidism have lower levels of vitamin B12. Since B12 deficiency and hypothyroidism share symptoms such as fatigue, muscle weakness, depression, memory problems, numbness and tingling, B12 deficiency is likely to be missed in these patients. The ensuing hyperhomocysteinemia on account of B12 deficiency may increase cardiovascular risk. Hence, these findings suggest that hypothyroid patients and even those with subclinical hypothyroidism must be routinely screened for B12 levels at the time of diagnosis and periodically thereafter, although current guidelines for hypothyroidism in adults make no such recommendations. The authors hope that their findings would “serve as a basis for the modification of clinical practice guidelines”.

Reference

1. Benites-Zapata VA, et al. Vitamin B12 levels in thyroid disorders: A systematic review and meta-analysis. Front Endocrinol (Lausanne). 2023 Feb 22;14:1070592. doi: 10.3389/fendo.2023.1070592.