Maternal hypothyroidism and fetal chondro-osseous development in rats.

The bone development of rat fetuses from female Wistar rats thyroidectomized prior to mating was studied, between 16 and 21 days of gestation. The parameters studied in each rat fetus were fetal weight, number of fetuses per litter, radiological data and frequency of appearance of ossification centers, diaphyseal radiological length of long bones, longitudinal ratio between epiphysis and diaphysis of long bones on cleaned and stained limbs, and volumetric tibial studies on the same limbs. Our results show a delay of fetal chondro-osseous development and a delay of weight increase in fetuses from thyroidectomized rats. After onset of fetal thyroid function, the fetal development begins a catch-up growth, which is not sufficient to completely overcome development delay prior to birth.