Risk of hypoglycemia associated with thyroid agents is increased in patients with liver impairment

To determine the risk of developing hypoglycemia from drugs that affect glucose homeostasis and evaluate the elevation of that risk by liver impairment as judged by a decrease of liver reserve or the severity of abnormal values in liver function tests.

A hospital-based case-control study was carried out. The base population consisted of all patients aged 20 years and older attending a university hospital in Japan from 2002 - 2004 who had received drugs and serum glucose measurements. Cases were defined as having had at least one episode of hypoglycemia as determined by a serum glucose concentration below 70 mg/dl. Up to 5 controls for each case were matched for the year of serum glucose measurement, out- or inpatient status, clinical departments visited, and age difference within 5 years, taken randomly from the base population without hypoglycemia. The odds ratio for developing hypoglycemia was estimated using conditional logistic regression analysis.

From a base population of 10,011, 245 cases and 1,194 controls were enrolled. Of the drugs investigated, levothyroxine use was associated with an increased risk of hypoglycemia in patients with liver impairment (adjusted odds ratio; non-use with normal liver (reference), non-use with liver impairment 0.91 (95% CI 0.62, 1.33), use with normal liver 4.50 (0.58, 34.76), use with liver impairment 14.68 (1.57, 137.4), p for trend 0.007). The risk elevation likely depended on the lowering of liver reserve.

Clinicians and pharmacists should carefully monitor serum glucose concentrations in levothyroxine users with liver impairment, especially those with lower liver reserve.