Bile flow to the duodenum is reduced in hypothyreosis and enhanced in hyperthyreosis.

Disturbances in sphincter of Oddi (SO) function may prevent normal bile flow and thus enhance probability of common bile duct stone (CBDS) formation. We have previously shown increased prevalence of diagnosed hypothyroidism in CBDS patients, which may be explained by thyroxine-induced inhibition of SO contractility, in addition to previously suggested changes in bile composition and hepatocytic excretion. The aim of this study was to investigate biliary dynamics in relation to altered thyroid gland function in rat, a rodent without a gallbladder. Euthyroid, hypothyroid or hyperthyroid Spraque-Dawley rats were anaesthetized with i.p. urethane, and exsanguinated at 15, 45, or 60 min after intravenous 99mTc HIDA injection. At these timepoints, the bile flow to intestine was determined by measuring the relative intestine vs. liver radioactivity. At 45 min this was 44% lower in hypothyroid rats and at 60 min 73% higher in hyperthyroid rats compared to euthyroid rats, while hepatic radioactivity at 15 min and blood pressure at injection were similar in the groups. We conclude that the bile flow to duodenum is reduced in hypothyreosis and enhanced in hyperthyreosis.