Liver Function in Cats with Hyperthyroidism Before and After¹³¹I Therapy

Abstract

Background:The clinical significance of high serum concentration or activity of markers of liver damage in cats with hyperthyroidism is unknown.Objective: To evaluate serum markers of liver function and damage, and ultrasonographic changes in cats with hyperthyroidism and with high liver enzymes, and to determine if abnormalities resolve after treatment with

The Prevalence, Magnitude, and Reversibility of Elevated Liver Enzyme Activities in Hyperthyroid Cats Presenting for Iodine-131 Treatment

“…In total, 123/217 (56.7%) had an elevation in ALT, 53/215 (24.7%) had an elevation in ALP, and 29/186 (15.6%) had an elevation in AST. This finding is lower compared to 75.0–78.9% shown in previous reports with fewer hyperthyroid cats ( 9 , 15 ). Our study is the first to report the magnitude of ELEZ in a large cohort of cats presenting for I-131 treatment, with ~8% of cats having ALT >500 IU/L.…”

“…A previous small prospective observational study showed that hyperthyroid cats can have normal liver function and no sonographic abnormalities within their livers despite ELEZ, and all the hyperthyroid cats in that study had NLEZ following I-131 therapy ( 15 ). In the present study with a larger cohort of cats, total thyroxine concentration had a positive correlation with liver enzyme activity elevations, and all cats with STFU or LTFU had NLEZ following euthyroidism after successful I-131 treatment.…”

“…A selection bias may have existed in the cats that were referred for I-131 therapy to our institution, as ill hyperthyroid cats with concurrent primary hepatobiliary disease may have not been considered for referral by the primary veterinarians. Our study did not include the measurement of plasma ammonia concentrations or paired fasted and post-prandial serum bile acid concentrations before and after I-131 treatment, and therefore, hepatic function cannot be assessed in our study; however, a previous study could not demonstrate hepatic dysfunction in hyperthyroid cats presenting for I-131 treatment ( 15 ).…”

“…In human thyrotoxicosis, ELEZ are common, with up to 76% of patients having at least one liver function test abnormality, and the ELEZ are often reversible once the patient achieves a euthyroid state, and there is also no correlation with histopathologic lesions and ELEZ ( 14 ). One study with 19 hyperthyroid cats treated with I-131 could not demonstrate an association with abnormalities in the sonographic appearance of the hepatic parenchyma or liver functional variables (serum bile acids, albumin, ammonia, cholesterol, and blood urea nitrogen) in hyperthyroid cats regardless of the degree of ELEZ (78.94% of the cats had ELEZ), and the liver enzymes (LEZ) in these cats after I-131 therapy had no significant difference with age-matched healthy control cats ( 15 ).…”

Diagnosis and management of feline hyperthyroidism: current perspectives

“… 25 – 27 Although previous recommendations included evaluating hyperthyroid cats with ALP or ALT activity >500 IU/L for concurrent disease, 2 , 14 , 15 further experience has revealed that the changes seen in the liver secondary to hyperthyroidism usually do not affect liver function testing, such as paired serum bile acids, so such testing may not be warranted. 28 In addition, histologic evaluation of the liver in cats with hyperthyroidism reveals nonspecific and mild changes, 4 and liver enzyme changes associated with hyperthyroidism usually return to within the reference interval with successful management of the disease. 29…”