Nonalcoholic fatty liver disease (NAFLD) in combination with low thyroid function is associated with an increased risk of all-cause and cardiovascular mortality, according to new research.
For the study, in The American Journal of Gastroenterology, Dr. Donghee Kim of Stanford University School of Medicine, in California, and colleagues examined data from the National Health and Nutrition Examination Survey (NHANES) III, which was conducted from 1988 to 1994.
In particular, they analyzed NHANES III-linked mortality data through 2015 on more than 10,000 participants. There were a total of 2,978 deaths, most commonly due to cardiovascular causes and cancer, during the median follow-up period of 23 years.
The prevalence of NAFLD, defined as ultrasonographically diagnosed hepatic steatosis without coexisting liver disease, was 33.9%, including 19.7% with moderate to severe steatosis.
Higher levels of thyroid-stimulating hormone (TSH) in the euthyroid state can negatively affect metabolic health, the researchers note. To examine its possible influence in this population, they compared levels of TSH within the normal euthyroid range. Subclinical hypothyroidism was defined as a TSH level of more than 4.5 mIU/L and low-normal as between 2.5 and 4.5 mIU/L/.
Low thyroid function was also associated with a higher risk for cardiovascular mortality in the entire population and in those with NAFLD. There was no such association in the non-NAFLD group.
The researchers conclude that although NAFLD in and of itself does not increase the risk of all-cause or cause-specific mortality, NAFLD with increasing TSH levels is associated with all-cause mortality, and particularly cardiovascular mortality.