RESUMEN
In human beings the thyroid gland is one of the largest of the endocrine organs. It is one of the earliest endocrine organs to be differentiated and has an important hormonal role in embryonic development. The importance of thyroid gland is to promote growth and development of the brain during fetal life and for the first few years of post-natal life[1, 2]. The purposes of present study are 1)to study the microscopic structure of the human thyroid in different gestational age groups of normal stillborn foetuses; 2) to correlate the size of thyroid follicles; the nature and amount of colloid content of thyroid follicles at different stages of development. The study was carried out on 50 stillborn normal human foetuses. The microscopic structure of thyroid was studied under light microscope. The study concluded the developmental staging of thyroid as: the precolloid stage; the colloid formation stage; the folliculogenesis stage; secretory activity stage.