Growth Hormone

What stimulates GHRH?

Exercise

Emotional stress

Physical stress

Hypoglycemia

Increased amino acids

Decreased FFA concentration

Testosterone

Estrogen

Thyroxine

What stimulates GHIH?

Growth hormone

High IGF-I levels

Hyperglycemia

High fatty acid concentration

Obesity

Senescence

Pregnancy

What replaces GH in pregnancy?

Placental GH

What is the ultra-short feedback loop relating to hGH?

Release of GHRH inhibits the release of more GHRH in the hypothalamus

What mechanism does hGH use?

Tyrosine kinase

What kind of hormone is hGH?

Protein

What is the most important hormone for normal growth up to adulthood?

hGH

T/F: hGH is secreted at a constant rate all day.

False - pulsatile pattern and burs

What additional molecule is needed in a growth hormone receptor

What is the result of hGH on the liver?

increase gluconeogenesis/glycogenolysis

increase IGF-1 production

What is the result of hGH on skeletal muscle?

increase AA and glucose uptake

What is the result of hGH on bone?

Increase glucose and AA uptake

• increase protein synthesis

• increase BMD

• chondrogenesis - bones grow in length

What is the effect of hGH on adipose tissue?

increase lipolysis

How does hGH increase lipolysis?

GH is going to trigger hormone sensitive lipase to cut triglyceride into glycerol and FA

When some of hGH goes to the liver, what does it stimulate the synthesis of?

IGF-I

What happesn when IGF-I binds to insulin receptors?

Increased glucose uptake

What affect does IFG-I have on muscles, bones, and cartilage?

Muscles - open channels for AA to enter muscle (protein synthesis)

Bone - increase osteoblasts/clasts

Cartilage - at epiphyseal plates

What effect does hGH have on bones?

Increase endochondral ossification and protein synthesis of collagen type 1

What effect does IGF-I have on cartilage?

Increase size, differentiation, and proliferation of chondroblasts

Increase linear growth

What are the other functions of hGH?

Increase plasma calcium

Increase immune response

Increase oxygen transport

How does hGH increase plasma calcium?

increase intestinal absorption of calcium

How does hGH increase the immune response?

increase number of structures

produce antibodies

How does hGH increase oxygen transport?

increase synthesis of erythropoietin

What is the term for excess hGH in adults?

Acromegaly

What are some causes of childhood hGH deficiencies?

Idiopathic

Head trauma

Damage to pituitary/hypothalamus

Brain tumor

Radiation treatment to head

Gene mutation

What is the MC cause of childhood hGH deficiencies?

Idiopathic

T/F: hGH deficiencies in children affect the child’s intelligence.

False - no effect at all

What are the complications of childhood hGH deficiencies?

Decreased energy level

Cardiovascular risk function

Decreased bone density

What is the cause of overproduction of hGH in children and youbng adults?

too much growth hormone released due to non-malignant tumor of somatotrophs

What is the MC tumor causing excess hGH in young adults and children?

Macroadenoma

What are the symptoms of overproduction of hGH in children and young adults?

unusually large growth during childhood before closure of long bone epiphysis

What is a sign of gigantism?

Fails to suppress GH

High prolactin levels

Increased IGF-1

What hormones are increased with gigantism?

GH

Prolactin

IGH

What is the most common pituitary adenoma causing hGH deficiencies in adults?

Prolacinoma

What mechanisms of action does GHRH use?

Adenylyl cyclase AND phospholipase C

What target tissue of hGH increases IGF-1 production?

Liver