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Growth hormone: a paracrine growth factor in embryonic development?
S Harvey1, C D Johnson, P Sharma
1Department of Physiology, University of Alberta, Edmonton, Canada.
Summary
Early embryonic growth may not depend on pituitary growth hormone (GH). Instead, extra-pituitary GH may act locally as a paracrine factor, influencing development in the early stages.
Area of Science:
- Developmental Biology
- Endocrinology
- Embryology
Background:
- Pituitary growth hormone (GH) is crucial for postnatal growth.
- Early embryonic and fetal growth are traditionally viewed as independent of pituitary GH.
- Chicken embryos show no detectable somatotrophs or serum GH until late embryogenesis.
Purpose of the Study:
- To review the potential role of extra-pituitary growth hormone (GH) as a paracrine factor in early embryonic development.
- To explore the hypothesis that embryonic growth may rely on local GH action rather than pituitary GH.
Main Methods:
- Review of existing literature on avian embryogenesis and GH.
- Analysis of studies involving decapitation and GH administration in chick embryos.
- Consideration of evidence for extra-pituitary GH production and action.
Main Results:
- Pituitary GH is not essential for early embryonic growth in chickens.
- Decapitation and pre-hatch GH administration show minimal impact on embryonic growth.
- GH can be produced and function in extra-pituitary tissues.
Conclusions:
- Early embryonic growth might be regulated by paracrine actions of extra-pituitary GH.
- Growth hormone may function as a paracrine growth factor during early development.
- Further research is warranted to elucidate the specific roles of extra-pituitary GH in embryogenesis.