Endocrine Abstracts

Introduction: The plasma vitamin B12 (B12) measurement is mainly conducted to detect B12 deficiency. But incidental finding of elevated B12 is not uncommon and may be a sign of serious disease, like solid cancers or caused by over-supplementation. However, there are cases in which high B12 levels are seen in the absence of supplements.

Case: A 57-year-old female presented to our outpatient endocrinology clinic with complaints of headache, hot flashes, dizziness and she was concerned about persistent high level of serum vitamin B12 (2058 pg/ml; 1795 pg/ml; 2521 pg/ml) without supplementation. Her medical history and the documentation she presented revealed that patient was diagnosed with scleroderma, and she has been treated for 25 years. She had autoimmune thyroid disease, impaired glucose tolerance test. In 2023 she had undergone brain aneurysm clipping. At present laboratory investigations, her thyroid function test was compatible with isolated hypothyroxinemia (TSH -2.6 mIU/ml; FT4- 8.98 ng/ml; FT3- 5.88 pmol/l). HbA1c – 5.1%, prolactine 8.33 ng/ml (4.79-23.3), low level of folate – 7.42 nmol/l ( 10.4-78.9); elevated homocysteine – 14.69 mkmol/l (<12.00). Paradoxic combination of hypercobalaminemia and hypercysteinemia got us confused. An MRI scan of the brain as well a CT scan of abdomen, gastroscopy and colonoscopy did not revealed any abnormalities as solid lesions; on an X-ray of chest was shown interstitial opacification suggestive of scleroderma lung disease. We hypothesized the possible pitfalls of measurement and interpretation of vitamin B12. Accordingly, we requested B12 measurement after PEG (polyethylene glycol) precipitation which showed normal concentrations of cobalamin.

Conclusion: Macro-vitamin B12 is an underestimated cause of supra-physiological cobalamin plasma levels and deserves appropriate attention to avoid potential erroneous clinical decisions.