Transcriptional Regulation of Growth Hormone Gene Expression by Growth Hormone-releasing Factor

Production and release of hormones by the pituitary is known to be under complex hormonal control. Prolactin, for example, is both positively and negatively regulated by steroid and thyroid hormones as well as by peptide hormones. Some hypothalamic releasing factors have been shown to regulate both hormone biosynthesis and hormone release. In the case of growth hormone (GH), glucocorticoids and thyroid hormone stimulate its production, at least in part by stimulating transcription of the GH gene, and somatostatin inhibits and growth hormone-releasing factor (GRF) stimulates its release. So far, however, polypeptide hormone regulation of GH biosynthesis has not been demonstrated. Recently a peptide with GH-releasing activity has been characterized from human pancreatic islet tumours. We report here that pure human pancreatic GRF (hpGRF) stimulates transcription of the GH gene, as well as stimulating GH release.