GLUCOSE-TOLERANCE AND INSULIN-SECRETION IN SPONTANEOUSLY HYPERTHYROIDCATS

Glucose tolerance and insulin secretion after administration of a gluc ose load were determined in 11 clinically normal cats and 15 cats with spontaneous hyperthyroidism. In six hyperthyroid cats, a glucose tole rance test was repeated after treatment with radioactive iodine (I-131 ). All cats had similar baseline glucose concentrations. However, the cats with hyperthyroidism had a significantly decreased glucose cleara nce, which was worse after treatment. Hyperthyroidism also caused a ma rked increase in basal and glucose-stimulated insulin secretion, which was not improved with treatment. It is concluded that hyperthyroidism in cats may lead to long-lasting alterations of glucose tolerance and insulin secretion which may not be reversed by treatment.