Inhibition of Hepatic Binding of Thyroxine by Cholecystographic Agents

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Abstract

Subsequent to studies indicating that cholecystographic agents and sulfobromophthalein (BSP) inhibit uptake of thyroxine (T4) by rat liver slices, the effect of such compounds on hepatic storage of T4 in man has been examined. After intravenous administration of [125I]T4 to five normal subjects, hepatic radioactivity, estimated by external gamma counting, rose to a peak in ∼4 h and then declined in parallel with serum radioactivity. When a 6-g dose of the cholecystographic agent, tyropanoate (Bilopaque), was administered orally 3 d later, estimated hepatic extravascular radioactivity fell 50-60% within 4 h and then rose toward the pretyropanoate value. Concomitant with the fall in hepatic radioactivity, serum radioactivity rose 57-70%, as did stable T4 levels in serum, suggesting that hormone discharged from the liver entered the serum. Both uptake of T4 and discharge by tyropanoate were much less in two patients with liver disease.

Authors

James V. Felicetta, William L. Green, Wil B. Nelp