Morphological and Endocrinological Characteristics of the Endocrine Systems in Wistar Hannover GALAS Rats Showing Spontaneous Dwarfs

Abstract

We found spontaneous dwarfs in Wistar Hannover GALAS rats, and morphologically and endocrinologically investigated the endocrine systems. Histologically, little colloid formation, decreased follicular size, and huge vacuoles in the follicular epithelium were observed in the thyroid of the affected animals. The vacuoles reacted positively for thyroglobulin. Electron microscopically, dilated rough endoplasmic reticulum, nuclear dislocation and few secretory granules were observed in the thyroid follicular cells. Serum triiodothyronine and thyroxine values were markedly low, whereas the serum thyroid stimulating hormone value was markedly high. These findings indicated that this dwarfism was caused by primary hypothyroidism.