Localization of iron and sulfur in the lysosomes of thyroid epithelium using electron probe microanalysis and X-ray spectrometry

Thyroid lysosomes have been studied by means of EPMA combined with an electron microscope. In 4 months old mice, lysosomes are a few number and contain very low iodine concentrations and sulfur load is not significant. In 10 months old mice, iodine only or associated with sulfur is observed in homogeneous lysosomes varying in size and density. Those two types of localizations reflect two eventual steps in hormonal metabolism pathway of iodine.