a histomorphometrical evaluation of the diameter of thyroid follicles at the proximal, middle, and distal extremities of the thyroid gland in dareshuri horses (equus caballus)

The parenchyma of the thyroid gland is comprised of cells arranged in a spherical follicle, surrounded by a dense network of capillaries. these cells exhibit a range of morphologies, from squamous to cuboidal. the present study investigates the differences in follicle diameter between the proximal, middle, and distal regions of the thyroid gland in horses. while preparing tissue samples from five female dareshuri horses and processing them in the histopathology laboratory of the veterinary faculty at shahrekord university, paraffin blocks were prepared using a microtome with incisions of 5 μm in thickness. the data obtained from the histometric evaluations of the proximal, middle, and distal regions of the thyroid gland revealed that the highest mean diameter of the small thyroid follicles was observed in the middle region, while the lowest mean diameter was observed in the distal end of the gland. the diameter of the large follicles reached their highest and lowest values, respectively, in the proximal and middle extremities of the thyroid gland. the results of this study indicate that there is a significant difference in diameter between the middle and distal extremities of the thyroid gland.