Liver Function in Cats with Hyperthyroidism Before and After 131I Therapy

Abstract

These results demonstrate that extensive examination for hepatobiliary disease in most cats with hyperthyroidism is unnecessary.

Feline Hyperthyroidism

“…The increases are usually only mild to moderate (less than 500 IU/L), although higher values are noted occasionally. Increases in gamma glutamyl transferase (GGT) have not been reported in hyperthyroid cats (Archer and Taylor, 1996;Berent et al, 2007). Hepatic hypoxia is thought to be the major cause of abnormalities in ALT but increased hepatic enzyme activity may also be due in part to malnutrition, congestive heart failure, infection, and direct toxic effects of thyroid hormones on the liver.…”

“…In addition to increased hepatic enzymes, cats with hyperthyroidism have significantly higher fasting serum ammonia concentrations than euthyroid cats; these values return to normal with effective treatment of the hyperthyroidism (Berent et al, 2007). The reason for increased ammonia concentrations is unknown, but it may be secondary to accelerated protein catabolism and deamination due to the increased metabolic rate.…”

“…Four of the 19 hyperthyroid cats evaluated had ALT concentrations greater than 500 I/L; however, the ALT returned to normal in all cats after treatment. Liver enzyme activities, regardless of their origin, usually return to normal with successful management of the hyperthyroidism (Berent et al, 2007). Other indicators of hepatic dysfunction may include hypoglycemia, hypocholesterolemia, hypoalbuminemia, and decreased blood urea nitrogen (BUN).…”

Creatine kinase serum activity in feline hyperthyroidism

“…Various causes of hepatocyte damage in animals with hyperthyroidism have been investigated, though little information is available for cats. Ultrastructural and functional changes in hepatocyte mitochondria have been documented in rats who are thyrotoxic including T3 associated mitochondrial-induced apoptosis and oxidative hepatic deoxyribonucleic acid damage because of lipid peroxidation, protein oxidation, and glutathione depletion (BERENT et al, 2007).…”

Feline hyperthyroidism: diagnosis and treatment

“…Nonetheless, no hepatic parenchymal or functional abnormalities are noted and liver enzyme activity becomes normal after induction of euthyroidism (Berent et al, 2007). When marked increases in liver enzyme activity occur in mildly hyperthyroid cats, an investigation for liver disease must be pursued, especially when they persist despite treatment.…”