EFFECTS OF 3-DAY ORAL CHOLECYSTOGRAPHY ON SERUM IODOTHYRONINES AND TSH CONCENTRATIONS - COMPARISON OF THE EFFECTS AMONG SOME CHOLECYSTOGRAPHIC AGENTS AND THE EFFECTS OF IOPANOIC ACID ON THE PITUITARY-THYROID AXIS

The effects of repeated doses of oral cholecystographic agents on serum thyroxine (T4), 3,3',5-triiodothyronine (T3), 3,3',5'-triiodothyronine (rT3) and thyrotrophin (TSH) concentrations were studied in 37 euthyroid male subjects. Iobenzamic acid, tyropanoic acid, iopanoic acid, and ipodate sodium, in a dosage of 3 g for 3 days, respectively, induced a significant decrease in serum T3 and an increase in rT3 within 24 hr after initial dose, followed by an increase in TSH and a slight increase in T4. The extent of the changes in rT3 varied between the agents, ipodate causing the greatest change, but without any relation to the changes in T3 and T4. Responses of serum T4, T3, rT3 and TSH concentrations to exogenous thyrotrophin-releasing hormone (TRH) and bovine TSH were also studied before and after 3-day doses of iopanic acid. In 11 subjects given iopanic acid, the response of TSH to TRH (500 μg, IV) was increased but the T3 response was unchanged. A dose of TSH (10 U.S.P. units, IM) caused a significant increase in serum T3 and a decrease in TSH concentrations in 5 subjects both before and after cholecystography.