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The prevalence of hypocobalaminaemia in cats with spontaneous hyperthyroidism
A K Cook1, J S Suchodolski, J M Steiner
1Department of Small Animal Clinical Sciences GI Laboratory, Texas A&M College of Veterinary Medicine, College Station, TX 77843, USA.
Objectives:
To determine the prevalence of hypocobalaminaemia in cats with moderate to severe hyperthyroidism and to investigate the relationship between cobalamin status and selected haematologic parameters.
Methods:
Serum cobalamin concentrations were measured in 76 spontaneously hyperthyroid cats [serum thyroxine (T(4) ) concentration ≥100 nmol/L] and 100 geriatric euthyroid cats. Erythrocyte and neutrophil counts in hyperthyroid cats with hypocobalaminaemia were compared with those in hyperthyroid cats with adequate serum cobalamin concentrations (≥290 ng/L).
Results:
The median cobalamin concentration in hyperthyroid cats was lower than the control group (409 versus 672 ng/L; P=0·0040). In addition, 40·8% of hyperthyroid cats had subnormal serum cobalamin concentrations compared with 25% of controls (P=0·0336). Weak negative correlation (coefficient: -0·3281) was demonstrated between serum cobalamin and T(4) concentrations in the hyperthyroid population, and the median cobalamin concentration was lower in cats with T(4) above the median of 153 nmol/L compared with cats with T(4) below this value (P=0·0281). Hypocobalaminaemia was not associated with neutropenia or anaemia in hyperthyroid cats.
Clinical Significance:
This study indicates that a substantial proportion of cats with T(4) ≥100 nmol/L are hypocobalaminaemic and suggests that hyperthyroidism directly or indirectly affects cobalamin uptake, excretion or utilisation in this species.
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