Impact of Age on the Thyroid Gland of Guinea pig at Different Stages

Abstract

The age-related changes in the thyroid gland are also progressive and structural and functional changes. Recognizing these changes that are normal with aging is crucial in differentiating normal changes in physiology from abnormal changes in thyroid gland. In the present study, the histological architecture of the thyroid gland in guinea pigs (Cavia porcellus) was investigated at various stages of life. Thirty-six clinically healthy guinea pigs were grouped into four age sets, juveniles (6 months), young (12 months), adult (24 months) and old (36 months). There was a high degree of thyroid age-related histomorphological changes. Juvenile group: the follicles were relatively small, follicular and parafollicular cells were poorly differentiated and there were wide connective tissue septa. The young group had well organized follicles with cuboidal epithelial cells and a lot of colloid, suggesting increased functional activity. Thyroid gland in the adult group exhibited enlarged follicles with abundant colloid and well developed glandular structure, indicating that thyroid gland was mature and stable functional. The old group on the other hand showed severe histological changes such as enlarged and irregular follicles with the presence of foamy colloid, flattening of the follicular epithelial cells, vascular congestion and degenerative changes in the glandular parenchyma. Histomorphometric assessment comprised follicular size and diameter, morphology of the follicular epithelial cells, distribution of the parafollicular cells, thickening of the basement membrane and organization of the interstitial connective tissue. Results have shown that the thyroid gland has different physiological activity during different periods of life and it has progressive modifications in its structure with ageing. Such changes could be responsible for changes in thyroid function and susceptibility for thyroid diseases in aging.