Growth Hormone Set 11

What does GH do?

What does GH do?

Stimulates linear growth in children by acing directly and indirectly via IGF-1 synthesis

What are specific metabolic actions of GH?

◦Increased lipolysis and lipid oxidation

◦Stimulation of protein synthesis

◦Antagonism of insulin action

◦Phosphate, water, and sodium retention

Describe the negative feedback of IGF-1

Hypothalamus reduces GHRH

Pituitary increases somaostatin

Circadian rhythm stress and cortisol fasting results in what being increased in the hypothalamus?

GHRH

Circadian rhythm stress and cortisol fasting results in what being decreased in the hypothalamus?

Somatostatin

Where is GH located?

Anterior pituitary

What’s a direct effect of GH?

Proliferation of chondrocytes

What’s a indirect effect of GH?

Target tissue production of IGF-1

What do the 6 IGF binding proteins (IGFBPs) do in circulation?

regulate free IGF - 1

What is the result of a deficiency of GH in kids?

Short stature

Too much GH causes (for kids)?

Gigantism

Too little GH (in adults) causes?

NO clinical syndrome

Too much GH (in adults) causes?

Acromegaly

Bones and tissues grow to quickly leading to enlarged hands and feet

HIGH normal hormone production correlates with…

EXCESS production

LOW hormone production correlates with…

DEFICIENCY state

If the is an overlap of tumor and HIGH normal values…..

Tumor values are not NOT suppressed

If there is an overlap of deficiency and LOW normal values

Deficiency values are NOT stimulated

What happens in normal hormone production?

Suppress Down

Stimulate UP

Compatible with an underproduction state

Lack of stimulation

Compatible with an overproduction state

Lack of suppression

What’s the best test for acromegaly?

IGF-1 concentration

Why is IGF-1 a better test for acromegaly vs GH?

GH jumps up and down throughout the day (15 min half life)

IGF-1 doesn’t vary, it has a longer half life (~ 22 hrs)

If IGF is high whats the next step to diagnose acromegaly?

• GH measurement after oral glucose suppression test

• Inadequate suppression confirms diagnosis

• Pituitary MRI to evaluate adenoma

MOST SPECIFIC test for acromegaly

Glucose suppression test

75 g glucose oral dose, measure at 2 hours

Normal = < 1 ng/mL

Acromegaly = > 1 ng/mL

How does GHD display in kids?

Can be congenital or acquires

Most important effect is growth failure

Must meet any of these results to be diagnosed:

• 2.5 SD below mean

• growth failure

• deficits in hypothalamic - pituitary hormones

How to treat Growth Hormone Deficiency (GHD)?

Synthetic GH

When should growth hormone stimulation tests be performed?

If IGF-I, IGFB-3 <10th percentile and delayed bone age

What provocative tests are recommended for GHD?

Clonidine, arginine, glucagon