Growth hormone Flashcards
Growth Hormone
Anabolic hormone that increases urinary nitrogen rentention while lowering serum urea leading to acquisition of muscle mass.
How does GH preserve plasma glucose level?
1) blocking glucose uptake by skeletal muscle
2) shunting muscle energy expenditure away from utilization of glucose to the oxidation of FFA
What are GHBP and IGFBP?
Cleaved products of receptors that bind to GH and IGF1 to increase their half life and lower renal clearance.
They are found in the liver.
What is the effect of GH and IGF on bone?
GH and IGF increase the IGF expression in chondrocytes and promote longitudinal growth.
GH and IGF increases the IGF expression in osteoblasts and promote deposition.
Where is GHRH released from?
Ventromedial nucleus of the hypothalamus
GHRH
Stimulatory factor that is secreted into the hypophyseal portal vessels and stimulate somatotropes in the anterior pituitary.
What receptors do the Somatotrophs express?
GHRH, GH secretagogue, dopamine, and somatostatin.
What stimulates GH secretion?
Hypoglycemia, arginine, ghrelin, dopamine and seratonin.
What’s the effect of a2 receptors on GH release
1) blocks somatostatin
2) stimulates serotonin which stimulates the somatotropes to release GH
When does GH level peak? What happens after?
Peaks at puberty around 20 years old then decreases 14% per decade.
What test is used to test for excess GH?
Suppresion test.
Oral glucose test is done by giving patient glucose and measuring blood GH. If it is higher than 2 ng/ml then it is excess.
Test given for GH deficiency
Stimulation testing using insulin, arginine, GHRH, and exercise
Treatment for Acromegaly
Somatostatin analogues: Octreotide and lanreotide inhibit GH secretion
Dopamine antagonisht such as bromocryptine and cabergoline since GH + PRL are coupled.
