MORPHOMETRIC STUDIES ON THE DEVELOPMENT OF THE HUMAN THYROID-GLAND .2. THE LATE FETAL LIFE

Histological and morphometric studies were performed on 27 thyroid gla nds obtained from normal fetuses ranging between 23 to 40 weeks of int ra-uterine life.In the thyroids the volume of gland, colloid, and stro ma were calculated by means of differential point-counting method and the height of the thyroid follicular cells was measured. Moreover, the epithelium/colloid ratio in the thyroid gland, a very sensitive param eter of stimulation of the glands by TSH, was calculated. Regarding th e values of this ratio in human fetal thyroid gland, the intra-uterine development of the gland may be divided into three distinct stages. T he first one, between weeks 10-18 is characterized by massive follicul ogenesis and gradual accumulation of the colloid. The second stage, be tween weeks 19-29 of fetal life is characterized by rather unchanged v alues of epithelium/colloid ratio and the size of follicles. The third stage, after the 29th week of development is characterized by a gradu al increase in the epithelium/colloid ratio and a decrease in the size of follicles.