7.5 Growth Hormones and Gonadotropins Flashcards
What is the target organ of growth hormone? What does it release in response?
Liver. Releases insulin-like growth factor.
Why isn’t getting fat necessarily the same as growing?
Growth necessitates net synthesis of proteins
How does cortisol influence protein synthesis?
Decreases it
Is foetal development influenced by growth hormones?
No; just placental hormones (GH-independent)
What type of hormone is growth hormone?
Peptide hormone
Which hypophysiotropic hormones regulate growth hormone secretion?
- GHRH
- GHIH
List some tissues that GH targets
- Skeletal muscle
- Bone
- Adipose
- Liver (primary site)
How does IGF influence GH secretion? How does it do this?
- Decreases GH secretion
- Increases GHIH secretion
What is another name for IGF-1? Where is it released? What does it do?
- IGF-1 = Somatomedin
- Released by liver
- Causes growth of bone and soft tissue
What do somatomedins promote? What type of hormones are they?
Peptide hormones that promote cell division
Are somatomedins only produced in the liver? What type of messaging do they use?
- No, they can be produced in other tissues
- Known to exert autocrine and paracrine effect in some instances (e.g. bone growth)
What is the relationship between IGF-1 and apoptosis
IGF-1 inhibits apoptosis
What is IGF-2?
Growth hormone that is preferentially expressed during embryonic development
Summarise JAK/STAT transduction
What factors influence growth?
- Nutrition
- Genetics
- Stress
- Growth hormones
When are the largest bursts of growth hormone in a 24 hour period?
During sleep
Where are somatomedins produced?
Liver (somatomedin = IGFs)
What type of changes can JAK/STAT transduction due to growth hormone binding produce?
- Metabolic changes
- Changes in gene transcription
What effect does growth hormone have on proteins
Increase synthesis, decrease degradation
What effect does growth hormone have on fat? How does this affect the level of free fatty acids in the blood?
Increases lipolysis (increasing blood free fatty acids)
What effect does growth hormone have on hepatic gluconeogenesis?
Increase
How does growth hormone decrease the amount of glucose going into muscles? What do they use instead of glucose? How does this influence blood sugar?
- Decreases insulin sensitivity
- Muscles use fatty acids
- Increased blood glucose
Effect of growth hormone on number/size of cells
Promotes hyperplasia and hypertrophy
List the effects of GH on bone growth
- Increased proliferation of periosteal osteoblasts (^ Thickness)
- Increased proliferation of epiphysial cartilage (and conversion of cartilage to bone)
- Increased bone remodelling
What secondary messenger do the gonads act on?
cAMP (same as kidney tubules with ADH/vasopressin)
Role of LH in males
Stimulates testosterone secretion
Role of FSH in males
Stimulates sperm production
Role of LH in females
Acute Surge: Ovulation
Maintains corpus luteum
Role of FSH in females
- Promotes follicle development
- Induces LH receptors on dominant follicle
- Stimulates estrogen secretion from follicles
Are androgens steroid hormones?
Indeed
Gigantism vs acromegaly
Gigantism: childhood
Acromegaly: after adolescence
What is the cause of gigantism?
Pituitary tumour/adenoma and hyperplasia in pituitary
Draw a mech of the action of growth hormone. Work out what potential issues could cause dwarfism
- Social/psychological
- Lack of GHRH
- Lack of somatottrophs
- Lack of GH receptors
- IGF secretion/production impaired
What is the difference between the ovarian cycle and the menstrual cycle?
Menstrual: Uterus
Ovarian: Ovaries
what is it called when ovarian follicles die off?
Atresia
Which structure releases inhibin? What does it do?
Released by corpus luteum, inhibits release of LH and FSH
