Influence of a single meal on fractional disappearance and catabolic rates of 3,5,3′-triiodothyronine and thyroxine over 24 hours

Abstract

1.1. The influence of a single meal on the rates of catabolism of 3,5,3′-triiodothyronine (T3) and thyroxine (T4) was investigated in young pigs. Plasma hormone concentrations, fractional disappearance rates (K), distribution volumes and catabolic rates were estimated during three periods after a meal.2.2. For T3, plasma concentration and K were greatest immediately after the meal and decreased progressively. Catabolic rate decreased from 0.45 nmol·hr−1·kg−1 immediately after the meal to 0.28 nmol·hr−1·kg−1 after 24 hr.3.3. In a separate investigation, a meal was found to cause an increase in plasma [125I] T4, indicating a shift in the distribution of the hormone pool. Catabolic rate of T4 appeared to be greatest in the period immediately after the meal and decreased to 0.43 nmol·hr−1·kg−1 nearly 24 hr later.