Ultrastructural aspects of the thyroid in a case of human congenital goitre with cretinism.

Transmission electron microscope and scanning electron microscope studies in a case of congenital goitre associated with cretinism revealed the existence of two cell types: the first with rounded endoplasmic cisternae and normal lysosomes; the second characterized by an abundance of lysosomes and/or lipofuscin granules. Intermediary aspects suggested that the second cell type was the progeny of the first type. As colloid droplets and apical pseudopods engulfing colloid were nearly absent, and as NBE127I was elevated in the plasma, it is suggested that iodoprotein secretion occurred by a process different from colloid phagocytosis as observed after acute TSH stimulation.