Effect of neonatal thyroidectomy on growth hormone secretion in the rat

Abstract

The influence of neonatal thyroidectomy (Tx) on GH production was investigated by means of Northern blot analysis. Tx resulted in a significant decrease in pituitary GH mRNA levels after 10, 15 and 20 days. The changes of pituitary GH mRNA were soon reflected in pituitary GH content. There was, however, no significant difference in pituitary GH mRNA levels and GH content between Tx and sham-operated rats at 5 days old. The pituitary GH cells were significantly decreased in number 15 and 20 days after Tx. These data suggest that GH mRNA is transcribed, independent of thyroid hormone, in the rat anterior pituitary gland during early neonatal life. In addition, the present study ascertained that GH dependence on thyroid hormone is acquired between the 5th and 10th day of neonatal life.