The Kinetics of the Thyroid Hormones and the Peripheral Conversion Rate of Thyroxine to Triiodothyronine in Acute Liver Insufficiency under Experimental Conditions

Summary

The kinetics of triiodothyronine (T₃) and thyroxine (T₄) were studied in 20 ewes. Ten were used as the control group, the other 10 received massive hepatic lesions induced by the ingestion of carbon tetrachloride. Half of each group were i.v. injected with ¹²⁵IT₃ or ¹²⁵IT₄, following a plasma disappearance over 96 hours. The amount of hormone present in each plasma sample was determined by immunoextraction procedure. The data was adjusted to the open two-compartment model

The hepatic insufficiency provoked a decrease in the disposition constant of T₃, an increase in the plasma half-life of the distribution phase as well as a moderately decreased turnover rate of this hormone.

The T₄ kinetics were altered during acute hepatic insufficiency in the decrease of the elimination constant K₁₃ and hormone plasma turnover rate.

The study of the peripheral conversion rate based on the kinetic data showed an extrathyroidal conversion of T₄ to T₃ in the control sheep, none being detected in the sheep with induced hepatic insufficiency.

Key-Words:

Kinetics - Acute Liver Insufficiency - Thyroid Hormones