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Endocrine 4
Growth Hormone, Insulin & Glucagon
27
Physiology
Undergraduate 3
11/26/2014

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Term
Where does somatotropin (GH) originate? What its role in young animals vs adults?
Definition
-originates from anterior pituitary
-promotes tissue & body growth in young animals
-regulates lipid & protein metabolism in adults
Term
Which hormones stimulate growth during fetal life?
Definition
IGF1 & IGF2

(Insulin-like Growth Factors)
Term
True or False

Growth hormones are not species specific, so it is common to use animal-sourced GH in humans with growth deficiencies
Definition
False

The protein sequence of GH is different between species, not compatible
Term
Which hypothalamic neurohormones stimlate/inhibit GH?
Definition
stimulate: GHRH
inhibit: GHIH
Term
How does GH regulate growth?
Definition
-stimulates production of IGF1 in liver
-IGF1 then stimulates cartilage & bone growth, milk production
Term
Which type of receptor does GH use?
Definition
cytokine (interleukin) family
Term
How is GH secretion regulated? What might increase secetion? (4) What inhibits secretion? (1)
Definition
-hypothalamus receives info from external stimuli & nutrients in blood

-increases during sleep (circadian rhythm)
-high AA low glucose in blood will increase GH secretion
-exercise & stress increase GH secretion
-sex hormones increase GH secretion (growth spurt at puberty)
-IGF1 causes negative feedback on GH secretion
Term
Describe the direct effects of Growth Hormone (4)
Definition
Anabolic: promotes protein synthesis

Catabolic: stimulates lipolyses & reduces lipogenesis
-lipolysis increase production of FA's

-also decreases glucose use in most tissues, increasing blood [glucose]
Term
Describe the indirect role of GH via IGFs (4)
Definition
-stimulates synthesis of IGF1 & its binding proteins in liver
-IGF1 stimulates proliferation of cartilage cells (chondrocytes) increasing bone growth
-stimulates satellite cells (muscle fibre growth)
-stimulates AA uptake & protein synthesis
Term
Describe the structure of IGF1 & what type of receptor it uses
Definition
-polypeptide chain, usually bound to carrier proteins
-acts via its one tyrosine kinase receptors
Term
Which has a longer half-life, GH or IGF1?
Definition
IGF1
Term
True or False

GH plays a major role in mammary gland development
Definition
false

It is involved with milk production, but not the growth of epithelial/secretory cells
Term
Describe the effects GH has on lactation
Definition
GH directs nutrients towards mammary gland for milk production rather than allow insulin divert them to lipogenesis for storage
Term
Why would bovine GH be used in milking cows? What is the human concern?
Definition
-can increase milk production 10% in early lactation, 40% in late lactation

Concern: bovine & human IGF1 have similar sequences, infants can absorb GH & IGF in the gut, this would alter their growth/development
Term
Describe some of the pathologies associated with GH
Definition
Overproduction of GH
-causes gigantism if it occurs before puberty
-causes acromegaly, increased bone width & density, diabetes after puberty

Lack of GH Production
-causes dwarfism
-mainly due to defects of GH or the GH receptor genes
Term
True or False

Dwarfism due to genetic defects of the genes responsible for GH production & GH receptors is an untreatable disease
Definition
False

Injections of recombinant GH and IGF1 can treat the issue
Term
Is the pancreas an endocrine or exocrine gland?
Definition
both
Term
What is the term for the endocrine regions of the pancreas?
Definition
islets of Langerhans
Term
What types of cells are found in the islets of Langerhans and what do they secrete?
Definition
beta cells: secrete insulin
alpha cells: secrete glucagon
Term
What is a preprohormone?
Definition
the initial product of translation, will need to undergo processing to be converted to a functional hormone
Term
Describe the synthesis & secretion of insulin
Definition
-produced as preprohormone, converted to insulin by removing a connecting (C)-peptide
-secreted, circulates free and is then degraded in target cells or in liver
Term
Describe the synthesis & secretion of glucagon
Definition
-29AA peptide produce as a preoprohormone which is converted to glucagon
-secreted, circulates free and is then metabolized in liver & kidneys
Term
Describe the actions of insulin (3)
Definition
-upregulates membrane glucose transporters, stimulating cellular uptake of glucose
-stimulates storage of glucose as glycogen in liver & muscle, TG's in adipose tissue
-stimulates AA uptake

Overall effects: decrease blood glucose & AA levels
Term
What is the major anabolic hormone of the body
Definition
insulin
Term
Describe the actions of glucagon (3)
Definition
-activates the enzyme responsible for glyocogenolysis in liver, triggering release of glucose
-stimulates gluconeogenesis in liver
-stimulates release of FAs from TGs in adipose tissue
Term
What regulates the release of insulin & glucagon? (4 points)
Definition
-primarily the concentration of glucose in blood
-AA concentration in blood to a small extent

-PNS activates insulin secretion during meals
-SNS inhibits insulin secretion & stimulates glucagon release when glucose levels drop
Term
What is diabetes mellitus? What is the difference between Type 1 and Type 2 diabetes?
Definition
hyperglycemia with increase glucose in urine

-blood glucose levels greater than ability of kidneys to reabsorb it

Type 1: insulin dependent
-insulin secretion is impaired

Type 2: insulin independent
-tissues are insensitive to secreted insulin
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