Growth Hormone Set 11

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

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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

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*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==

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%%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)

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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

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75 g glucose oral dose, measure at 2 hours

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Normal = < 1 ng/mL

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Acromegaly = > 1 ng/mL

How does GHD display in kids?

Can be congenital or acquires

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*Most important effect is growth failure*

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Must meet any of these results to be diagnosed:

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* > 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

What provocative tests are recommended for GHD?

Clonidine, arginine, glucagon