GROWTH-HORMONE - A PARACRINE GROWTH-FACTOR IN EMBRYONIC-DEVELOPMENT

Although pituitary growth hormone is obligatory for normal postnatal g rowth and development, early embryonic and fetal growth is generally c onsidered to be independent of pituitary GH. Indeed, in chickens, soma totrophs and serum GH are not detectable until late in embryogenesis, and neither partial decapitation nor pre-hatch GH administration great ly affects embryonic growth. However, since it is now known that GH ca n be produced and act in many extra-pituitary tissues, early embryonic growth may be independent of pituitary GH but dependent upon the para crine actions of extra-pituitary GH. The possibility that growth hormo ne may be a paracrine growth factor during early development will ther efore be considered in this brief review, which is based on the embryo genesis of the domestic fowl. (C) 1998 Published by Elsevier Science I nc. All rights reserved.