Extrapituitary growth hormone and growth?

Area of Science:

• Endocrinology
• Developmental Biology
• Molecular Biology

Background:

• Pituitary growth hormone (GH) is essential for postnatal growth but not for embryonic development.
• Embryonic growth is thought to rely on local growth factors rather than pituitary GH.
• The GH gene is expressed in extrapituitary tissues during early development.

Purpose of the Study:

• To review the expression and functional relevance of extrapituitary GH during embryonic growth.
• To investigate the role of local growth factors in early development.
• To explore the mechanisms of GH action in early development.

Main Methods:

• Review of existing literature on extrapituitary GH expression and function.
• Analysis of GH and GH receptor (GHR) gene expression patterns.
• Examination of studies involving GH immunoneutralization or production blockade in embryos.

Main Results:

• Extrapituitary GH expression occurs early in development, preceding pituitary GH.
• GH receptor (GHR) gene expression mirrors GH expression in extrapituitary tissues.
• Impairment of embryonic GH leads to growth defects and apoptosis in various species.

Conclusions:

• Extrapituitary GH likely mediates embryonic growth through local autocrine/paracrine mechanisms.
• The GH gene's persistent extrapituitary expression suggests ongoing postnatal roles.
• Understanding extrapituitary GH is key to comprehending early developmental processes.