Effect of perchlorate and methimazole on iodine metabolism.

Abstract

ABSTRACT The increment in urinary iodide excretion was compared, in normal and thyrotoxic subjects, during the baseline state and after administration of potassium perchlorate or methimazole. In the normal subjects, perchlorate administration produced increments of urinary iodide that appear to be equivalent to hormonal iodine secretion per day. Urinary iodide excretion was increased to 2.2–2.8 fold this level by methimazole This result is interpreted as compatible with extensive intrathyroidal recirculation of iodotyrosine iodide and leakage of a small fraction of this iodide to the blood in normal subjects. In thyrotoxic subjects, the average increment in iodide excretion produced by perchlorate was 464 μg/day. Methimazole augmented urinary iodide excretion 2.2 fold the level found with perchlorate, indicating that there is extensive conservation of intrathyroidal iodide in thyrotoxicosis. The technique allows a qualitative estimation of efficiency of reutilization of intrathyroidal iodine.