Metabolic clearance and production of diiodotyrosine in healthy man

Abstract

Metabolic clearance rate (MCR) and daily production rate (PR) of diiodotyrosine (DIT) were estimated using a constant infusion technique of trace amounts of [125-I]-DIT followed by chromatographical isolation of tracer. Median DIT MCR was in eight healthy subjects estimated to 162 l/day×70 kg (range 135-242), whereas PR was 52 nmol/day×70 kg (range 25-126). The median serum DIT concentration was 0.27 nmol/l (range 0.16-0.62). In five L-thyroxine substituted subjects without endogenous thyroxine (T4) production, serum DIT concentrations were below 0.02 nmol/l, suggesting that more than 94% of daily produced DIT is secreted by the thyroid gland.

Key Words:

• diiodotyrosine
• tracer kinetics