Growth Hormones Flashcards
What do growth hormones do?
Promotes skeletal growth in children and muscle development/bone maintenance in adults
What are the direct affects of GH on fat cells?
Fat cells, for example, have GH receptors. This stimulates them to break down triglyceride and suppresses their ability to take up circulating lipids.
What are some indirect affects of GH - what is this mediated by, secreted from and promotes?
Mediated primarily by insulin-like growth factor-1(IGF-1),secreted from the liver and other tissues in response to GH. Most of the growth promoting effects of GH are due to the IGF-1.
Why are males bigger than females?
Males tend to have more or more distinct pattern of growth hormones and this is why men are taller than females.
What happens if you have too little GH?
You tend to be shorter but you will be in proportion.
Where is GH made and how is it secreted?
GH is made in the somatotrophs in the pituitary gland. They are packaged into neurosecretory vesicles and secreted by calcium-dependent exocytosis. They enter the blood stream and plasma concentrations decay in 10 mins.
When is GH normally secreted and how is GH secretion altered?
Normally secreted in sleep and measured by radioimmunoassay
Excersise is also a potent cause of increased GH (probably cause GH helps muscle growth in adults)
Diet can also increase GH
Ageing decreases GH
What are symptoms of a GH deficiency?
Decreased energy, social isolation, depressed mood, increased anxiety
What are clinical features of a GH deficiency?
increased body fat, decreased muscle mass, impaired cardiac function, decreased insulin sensitivity and impaired glucose tolerance.
How does the hypothalamus control GH? (this is long)
Mainly secretes peptides and synthesized in the hypothalamic neurons. Hormones are released by exocytosis from neurosecretory endings, into blood vessels at the median eminence and transported to the anterior pituitary.
Act via specific membrane receptors on sub-populations of anterior pituitary endocrine cells.
GH comes from the anterior pituitary which gives you too points to modulate how much GH comes from the hypothalamus
What hormones control GH in the hypothalamus?
GH releasing hormone (GHRH) which is a peptidesynthesisedbyneuronesin theacruatenucleus of the hypothalamus and released from neurosecretory terminals at the median eminence.
Where is somatostatin secreted and why is it different in males and females?
Secreted in the periventricular nucleus and sexual dimorphism of theoestrogenreceptors could explain why there is different patterning in both GH and somatostatin in different genders.
How does GH patterning change with age and puberty?
Before puberty GH is secreted regularly
After puberty the pulses and smaller and further apart
In male rats GH pulses were fewer but larger than female rats
Why are pulsatilie things hard to measure?
as you need to take enough of the sample at regular intervals to get the full picture.
Why is GH patterning important for growth?
It helps with saturation e.g. if you give 9 mls of GH at once most wont be able to get in but if you give 3mls three thimes a day by the time your on your second or third dose the cell will be able to take it in
