Gross, histomorphological and histochemical changes in thyroid gland of goat with age. IV. Histomorphological study.

Histomorphological changes on the thyroid gland of 26 goats of different ages ranging from 20 days to over 5 years and of both the sexes were studied. The main fibroarchitecture was of collagen and reticular fibres, the latter fibres being gradually replaced by former with advancing age. The presence of thyroid lobule was observed in all age groups. The interfollicular connective tissue was constantly found around the follicle and increase with age. The follicles became irregular in outline and their diameter increased in the older subjects. The follicular epithelium comprised of two types of cells--Follicular cell and light cell and had tendency to become squamous with ageing. The mitotic division was occasional in younger and rare in older age groups. The mode of secretion was of merocrine and apocrine type. The solid form of colloid was observed in oldest goat. Accessory thyroid tissue and isthmus had similar histomorphology, however, the glandular sthmus was replaced by fibrous tissue with ageing.