Urinary Excretion of Unconjugated and Conjugated 3,5-Diiodothyronine

Summary

A radioimmunoassay for the estimation of 3,5-diiodothyronine (3,5-T₂) in human urine has been established. The urinary excretion of both glucuronide and sulfate conjugates of 3,5-T₂ were estimated after enzymatic deconjugation. In 19 healthy controls the median excretion of unconjugated 3,5-T₂ was 276 pmol/d, whereas the median excretion of glucuronidated and sulfated 3,5-T₂ in 7 healthy subjects was 448 and 451 pmol/d, respectively. The median excretion of 154 pmol/d in 9 hypothyroid patients did not differ from that found in controls. In contrast 12 patients with hyperthyroidism had an enhanced excretion, 1312 pmol/d (P < 0.01). Compared with previous data on the daily degradation of 3,5-T₂, it is concluded that approximately onesixth of degradated 3,5-T₂ is excreted in the urine.

Key-Words:

Urinary Excretion - 3,5-Diiodothyronine - Conjugates