Growth Hormone
- functions
- regulation of expression
- consequences of overexpression
- consequences of underexpression
- signalling pathways
- structure
Function
Growth hormone causes growth
- acts on the liver to induce IGF-1 expression
- increases muscle mass
- decreases glucose utilization, opposing insulin
- increases lipolysis and fat mobilization
Both growth hormone and IGF-1 provide negative feedback.
Regulation of Expression
Growth hormone releasing hormone (GHRH) and somatostatin stimulate and inhibit, respectively, growth hormone releasing cells in the anterior pituitary.
Ghrelin, secreted by gastric neuroendocrine cells, are elevated during fasting and stimulate GH secretion by acting on the hypothalamus and pituitary.
Consequences of Overexpression
Too much GH results in acromegaly, is what is responsible for the giants we've known - people 7 ft tall and higher.
Consequences of Underexpression
Growth hormone deficiency can cause pituitary dwarfism.
Signalling Pathways
Both PRL and GH have similiar affinities for the PRL receptor.
Structure
Prolactin is a 199 amino acid hormone with 16% homology to growth hormone.