Serum Cobalamin and Methylmalonic Acid Concentrations in Hyperthyroid Cats Before and After Radioiodine Treatment

• Published in: Journal of veterinary internal medicine Vol. 30; no. 2; pp. 560 - 565
• Main Authors: Geesaman, B.M., Whitehouse, W.H., Viviano, K.R.
• Format: Journal Article
• Language: English
• Published: United States J.B. Lippincott 01.03.2016; John Wiley and Sons Inc; Wiley
• Subjects: Animals; Cat Diseases - blood; Cat Diseases - therapy; Cats; Feline; Female; Hyperthyroidism - therapy; Hyperthyroidism - veterinary; Hypocobalaminemia; Iodine Radioisotopes - therapeutic use; Male; Methylmalonic Acid - blood; MMA; SMALL ANIMAL; Thyroxine; Vitamin B 12 - blood; Vitamin B 12 Deficiency - blood; Vitamin B 12 Deficiency - veterinary; Vitamin B12; MMA; Hypocobalaminemia; Vitamin B12; Feline; Thyroxine
• ISSN: 0891-6640; 1939-1676
• DOI: 10.1111/jvim.13918

BACKGROUND: Hyperthyroidism, the most common endocrine disorder in cats, has been associated with low serum cobalamin concentrations. Whether this is a functional cobalamin deficiency of clinical importance has not been assessed. HYPOTHESIS/OBJECTIVES: Cats with hyperthyroidism experience a functional cobalamin deficiency which correlates with their clinical catabolic state and is reversible with return of the euthyroid state. ANIMALS: Thirty‐nine client‐owned hyperthyroid cats. METHODS: Prospective observational study. Serum cobalamin, methylmalonic acid, and clinical scores were determined in each hyperthyroid cat at enrollment and when euthyroid (60 days after radioiodine treatment). RESULTS: Five of the 39 hyperthyroid cats (13%) had a low serum cobalamin concentration ranging from <150 to 290 ng/L. Serum cobalamin concentrations normalized to >350 ng/L in 2 of the hypocobalaminemic cats once euthyroid. None of the hyperthyroid/hypocobalaminemic cats had increased serum methylmalonic acid concentrations (175–601 nmol/L). In cats with clinical and biochemical hyperthyroidism, there was no correlation between serum cobalamin concentrations with total T4 concentration (P = .12) or clinical scores including body weight (P = .11) and BCS (P = .54). CONCLUSIONS AND CLINICAL IMPORTANCE: In this population of hyperthyroid cats, the prevalence of hypocobalaminemia was low. Specifically, hyperthyroid cats, in which concurrent gastrointestinal disease is unlikely. Hypocobalaminemia is not a functional deficiency requiring supplementation in hyperthyroid cats without gastrointestinal disease.