The thyroid gland is the first glandular structure to form and develops as a ventral midline as endodermal diverticulum from the floor of the foregut. The thyroid gland regulates the physical and chemical processes that occur at the cellular level. Thyroid hormones directly involved in the mammalian metabolism by a thermogenic in turns increase the amount of heat produced at a given time accelerating body growth and development and increasing cardiac function. The interrelationship of thyroid glands with body-growth and marked variations takes place viz in location, gross, histological and follicular activity during prenatal life.