Lecture 16 (GH and IGF)

Where is growth hormone (GH) made

Anterior pituitary

What is GH regulated by?

-GHIH (inhibitory)

-GHRH (releasing)

What are three metabolic actions of GH?

1. Protein metabolism

2. Carbohydrate metabolism

3. Lipid metabolism

How does GH affect protein metabolism?

-Increases AA uptake

-Increases protein synthesis

-Increases muscle mass

How does GH affect carbohydrate metabolism

-Increases blood glucose

-Increases hepatic glucose output

-Increases insulin resistance

-Decreases glucose uptake by muscle and fat

How does GH affect lipid metabolism?

-Increases lipolysis

-Decreases fat synthesis

-Decreases adipose mass

How is growth hormone related to age?

-GH secreted throughout life but rate decreases with age

-May account for loss of muscle mass and increase in adipose tissue in older animals

Insulin-like growth factor 1 (IGF-1)

Puts glucose into bloodstream (opposite affect from insulin)

Where is IGF-1 produced?

Liver

How do GH and IGF-1 work together?

GH directly causes an effect while IGF-1 is stimulated by GH and will cause an indirect effect

Bovine somatotropin (BST)

GH in cows used to increase milk yield

What public health issues are there with BST?

-Effects of increased BST and IGF-1 in milk in humans

-Mastitis and other problems causing increased use of antibiotics

-Allergic reactions to changes in milk protein composition

Is there any effect of BST in humans?

Bovine BST is not shown to cause any biological affect in humans

Porcine somatotropin (PST)

-Produce naturally by pituitary gland in pigs

-Acts as a growth regulator

Effects of PST injections in pigs

-Increase cell division in muscle tissues

-Decrease fat storage

-Increase protein accumulation

-Improve feed efficiency

What are some diseases involving excess GH production?

-Developmental hypersecretion (gigantism)

-Adulthood hypersecretion (acromegaly)

Developmental hypersecretion (gigantism)

Rapid, prolonged bone growth and normal body proportions

Adulthood hypersecretion (acromegaly)

-Abnormal body proportions

-Affects soft tissue of face, bones of face. and limbs (cannot affect long bones since they are already fused)

What are some diseases caused from too little GH?

-Panhypopituitarism

-GH deficiency

-GH resistance

-Adult GH deficiency

Panhypopituitarism

-Low functioning pituitary

-Causes dwarfism, slow bone and organ growth, reduced adult size and abnormal body conditions

GH deficiency

-Pituitary gland makes too little GH

-Causes skin inflammation and hair loss

GH resistance

Pituitary functions properly but receptors in target tissues do not respond to GH

Adult GH deficiency

-Animal is fully grown but cannot produce adequate amounts of GH

-Causes dermatosis

Why is too much GH associated with diabetes mellitus?

Leads to insulin resistance and an increase in blood glucose