Growth Hormone Flashcards
How can protein hormone (ex: growth hormone) secretion be controlled?
(Hint: 3 general ways)
mRNA level: transcription, splicing
Protein level: cleavage, modification
Secretion level: stimulus, amount released from storage
What brain structure synthesizes and secretes the growth hormone?
The anterior pituitary.
How does growth hormone have a direct biological effect?
Metabolism: helps break down fatty acids and also synthesize protein.
How does growth hormone have an indirect biological effect?
Growth: stimulates the liver (and other tissues) to produce IGF-1, promoting growth.
How does growth hormone increase protein synthesis (as a direct effect)?
By increasing the amino acid uptake and accelerating transcription/translation of mRNA.
What effect does growth hormone have on insulin?
Suppresses the ability of insulin to both stimulate glucose uptake in tissues and enhance glycogen synthesis in the liver.
What 2 hormones are inhibited by somatostatin?
- Growth hormone
2. Thyroid stimulating hormone
What hormone stimulates the synthesis and release of growth hormone? What brain structure secretes this?
Stimulated by growth hormone releasing hormone, which is secreted from the hypothalamus.
What tissue produces ghrelin? Where does this bind? What effect does this have on growth hormone?
Released from the stomach when empty. Binds to (secretagogue) receptors on somatotrophs and stimulates the secretion of growth hormone.
How does the stimulation of IGF-1 by growth hormone have an effect on the growth hormone axis?
IGF-1 acts on the pituitary by negative feedback and also stimulates the production of somatostatin (inhibits growth hormone production).
The release of growth hormone from the pituitary acts on the hypothalamus to inhibit the secretion of growth hormone releasing hormone by negative feedback. What other effect does this have?
It also acts by autocrine signalling in a negative feedback loop on itself.
What can we do to cause an increase in growth hormone?
stress (from exercise) and sleep, as well as increased protein consumption.
What can we do to cause a decrease in growth hormone?
Consume sugars and fats, or get old
At what age do growth hormone levels generally drop in humans?
30 years old.
How is growth hormone released (physically)? When during the day does the greatest release of growth hormone occur?
Released in a pulsatile patter, with the largest release coming just after the onset of deep sleep.
How does the presence of thyroid hormone influence the effect of growth hormone? What about the other way around?
They exhibit cooperativity/synergy. Together they have a much greater effect than they would individually.
Besides growth hormone deficiency, what else can lead to reduced growth?
Hypothyroidism can stunt growth even more than lack of growth hormone.
How is tyrosine kinase associated with cytokine receptors?
The cytokine receptor does not have any integrated tyrosine kinase, but rather recruits accessory proteins with a tyrosine kinase domain.
What kind of receptor does growth hormone bind to?
Cytokine receptors.
In which 5 tissues is growth hormone receptor expressed?
- Liver
- Muscle
- Bone
- Kidney
- Adipose tissue
How does growth hormone move around the body?
In the bloodstream bound to growth hormone binding protein (for stability, specificity, etc.)
What does growth hormone binding protein resemble (structurally)?
It’s actually just a growth hormone receptor without a membrane anchor (made by alternative splicing)!
What is an interleukin?
A type of cytokine which binds to a similar receptor as growth hormone.
How does the growth hormone receptor complex bind growth hormone?
Similar parts of the two receptor molecules bind two distinct regions on the growth hormone.
