Critical analysis of the histomorphometry of rat thyroid after treatment with thyroxin and propylthiouracil

The morphological variations of rat thyroid follicles after treatment with either thyroxin or propylthiouracil were evaluated by histomorphometry. A silver impregnation technique allowed a precise visualization of thyroid follicles on histological sections. The histomorphometric values (cell height, follicular diameter, percentage of epithelial cells) were obtained using a semi-automatic image analyser. The statistical tests used were analysis of variance (Fisher's test) and the Newman-Keuls tests. The results obtained showed that thyroxin treatment did not lead to any modification in histomorphometric values. Propylthiouracil, on the contrary, caused profound alterations in the morphology of thyroid follicles and in particular an increase in the height of the follicular epithelium. These changes were induced by a deficiency in thyroid hormones leading to an increase in thyroid-stimulating hormone (TSH) release. This study shows that with rigorous methodology, histomorphometry is adaptable to the requirements of a simple and reproducible evaluation of substances capable of causing functional perturbations and their effects on the thyroid gland.