Detection of elements in the lumen and the follicle cells of the thyroid gland of the horse by x-ray microanalysis.

The follicle epithelial cells of the thyroid gland from three horses were subjected to x-ray microanalysis to identify directly the distribution of iodine and other elements. The scanning transmission electron micrograph of the thyroid was directly correlated with the distribution of these elements detected by energy dispersive x-ray microanalyzer. Higher level of I, S, P, and Cl was detected in the intracellular granules while the luminal substance contained less I, S, Cl and little, if any, P. Data presented here might be evidence to support the condensing process of iodine in the follicle being absorbed into the intracellular droplet and then be concentrated further in the lysosomal granules.