Hepatic parenchymal tissue is known to be one of the major sites of thyroid hormone metabolism as well as glucagon action. Alterations in circulating thyroid hormone concentrations, as well as hyperglucagonemia, are well documented in subjects with hepatic cirrhosis and advanced liver dysfunction. Also, we have documented recently that hyperglucagonemia induced in normal subjects alters thyroid hormone metabolism, with lowering of serum T3 and a rise in serum reverse T3 (rT3) levels. Thus, it is conceivable that rising glucagon concentrations are responsible for altered thyroid hormone levels in hepatic cirrhosis. To examine this hypothesis, this study determined relationships between plasma glucose, glucagon, insulin, and insulin:glucagon ratio on one hand, and thyroid hormone concentrations on the other, in 51 subjects with hepatic cirrhosis. Significant negative correlations were noted between plasma glucagon and serum T3 (r = -0.418, p less than 0.001) as well as T3:T4 ratio (r = -0.627, p less than 0.0001), whereas significant positive correlations were observed between plasma glucagon and serum rT3 (r = 0.504, p less than 0.001) as well as rT3:T4 ratio (r = 0.644, p less than 0.0001). No such significant relationships were noted between either insulin, glucose and insulin:glucagon ratio on one hand and any of thyroid hormone indices on the other. Therefore, this study indicates that, in hepatic cirrhosis, circulating glucagon concentrations may play a major contributing role in induction of altered serum thyroid hormone concentration by influencing thyroid hormone metabolism.