Morphological Investigations of the Thyroid Gland in Dogs

Abstract

The present study aimed to comprehensively examine the thyroid glands of young and mature male dogs through anatomical, ultrasonographic, computed tomography (CT) imaging techniques, histological, and immunohistochemically. five male dogs were used. Grossly, the thyroid glands of dogs consist of two separated lobes that are localized on the lateral aspect of the cranial part of the trachea. Both lobes appeared as dark red flattened ellipsoid bodies. The right lobe was localized more cranially than the left lobe. Ultrasonography revealed the thyroid glands as a hypoechoic organ, but it was also more echogenic or isoechoic than the surrounding muscles. CT imaging provided high-resolution images for evaluating the gland’s morphology and any potential pathological changes. Histologically, the dog's thyroid gland was covered with a thick capsule, while the trabeculae of the gland are poorly expressed. Thousands of follicles represent the Parenchyma of the gland within the collagenous capsule, The shape of the thyroid follicle ranged from spherical to elliptical. Immunohistochemicals showed a strong positive reaction for TTF1 in follicular cells at a young age and moderate reactions in adult animals and this result might be associated with the physiological role of TTF1 in the differentiation of endodermal origin follicular cells into active endocrine cells. Similarly, immunostaining showed a stronger reaction for SYN in the parafollicular cells of young age than that of adult animals and this result might be associated with the physiological roles of SYN in the differentiation of neuroectodermal origin parafollicular cells into endocrine cells