Histological and Microchemical Studies on the Lipin Content of the Human Thyroid.

Abstract

The lipoid droplets found in the epithelial cells of normal human thyroids are the products of the secretory activity of these cells. According to their staining reactions they seem to consist mainly of mixtures of phospholipins. They are discharged into the colloid where they become gradually dissolved. The cells excrete the lipoids in the form of small droplets and granules which are suspended in larger drops of a watery substance that does not take the fat stains. The fat droplets are soluble in ether, alcohol and acetone, but insoluble in chloroform. They stain blue or bluish violet with nieblue sulfate, and black with the Lorrain Smith method. Some of them are stained after the Caccio's method. In older persons also clusters of larger fat drops are given off by the epithelium. These drops dissolve only in hot ether and are usually Caccio positive. A desquamation of cells filled with fat is relatively rare. The excretion of the lipins starts after the first year of life and increases with the age. But also in younger individuals much fat is occasionally found in the colloid. What influences the intensity of the lipoid excretion is not yet quite understood. Diseases seem to have no effect. In pronounced exophthalmic goiter, in tuberculosis of the thyroid, and in malignant adenomas fat is usually absent from the epithelium and the colloid. Lipid granules are also observed in the stroma of the thyroid. They give the same microchemical reactions as do the fatty substances in the epithelium and colloid. They are engulfed by flat and branched cells.