DISORDERS OF GROWTH Flashcards
What is growth defined as?
Increase in:
Anabolism Cell size and number Cell mutation and maintenance Organ size Body size and weight
Where is growth hormone released from?
Anterior pituitary
What is released in response to growth hormone?
The actions of growth hormone are mediated by insulin-like growth factors released from the liver.
Where does growth in the bones of children occur?
At the epiphyseal growth plate.
What is another name for growth hormone (GH)?
Somatotrophin
What are the two hormones responsible for regulating the release of growth hormone?
Growth-hormone releasing hormone (GHRH)
Somatostatin (also called growth-hormone inhibiting hormone, GHIH)
How is the release of growth hormone releasing hormone related to glucose levels?
Increased in levels of low glucose - this includes during sleep.
How is growth hormone transported in the blood?
GH-binding protein
At a cellular level, where does growth hormone act?
G-protein and JAK receptors on cell surface of target cells.
Which is the most important insulin-like growth factor as a stimulator of growth?
IGF-1
What effect does insulin like growth factor have on glucose levels in the blood?
IGF is antagonistic to insulin in terms of regulating glucose. IGF prevents glucose uptake and causes glycogen breakdown.
What is the effect of IGFs on bones before puberty?
IGFs stimulate chondrocytes in the epiphyseal growth plate to grow and divide.
The abnormal secretion of which hormones can lead to growth problems?
Growth hormone Insulin ADH Parathyroid hormone and vit D Cortisol Sex steroids Thyroid hormone (low levels causes growth problems)
What is the effect of thyroid hormone on growth?
T3 stimulate cell metabolism, promoting growth, especially in the CNS and bones.
T3 also stimulates GH secretion from the anterior pituitary.
What is the effect of cortisol on growth?
Inhibits GH release from pituitary
What is the disorder of excess GH secretion prior to epiphyseal fusion called?
Gigantism
What is the disorder of excess GH secretion after epiphyseal fusion called?
Acromegaly
What is the common complication associated with gigantism and acromegaly?
Glucose intolerance and diabetes. GH is antagonistic to insulin.
Do people with acromegaly get taller?
No. They epiphyseal growth plates have fused so no gain in height occurs.
What are the clinical features of acromegaly?
High blood pressure Cardiomegaly Enlarged head circumference Coarse thick skin Large lower jaw Spaces between lower teeth Large nose Large tongue Organomegaly (liver, kidneys) Large hands Large feet Hypercalcaemia Diabetes Osteoarthritis Sweating Irregular periods Sub fertility
Why might people with acromegaly lose their peripheral vision?
Pituitary tumour compresses the optic nerve
Why does acromegaly hold an increased mortality?
Cardiovascular disease
Respiratory disease
Malignancy
What is the most common cause of acromegaly?
Pituitary adenomas
What investigations would you do in someone who presents with the features of acromegaly?
Blood tests to look for raised IGF
GH levels following an oral glucose tolerance test - should decrease levels to less than 0.5
CT or MRI to investigate pituitary tumour
How do you manage someone with acromegaly?
The mainstay is surgical removal of the tumour. If surgery is unsuccessful or contraindicated then medical management can be attempted. This includes somatostatin analogue (octreotide), GHIH and recombinant GH analogue which works as a competitive antagonist. Radiotherapy may also be attempted.
What is the most common cause of dwarfism?
Deficiency of GHRH from the hypothalamus.
What are the stimulation tests used to assess GH deficiency in dwarfism?
GH levels post sleep
Hypoglycaemia levels (induced by insulin - not used frequently due to dangers)
Arginine stimulation test
How are patients diagnosed with dwarfism managed?
Subcutaneous injections of recombinant human growth hormone before sleep each night.
What are the somatostatin analogues that can be used in someone in acromegaly?
Octreotide
What must a random growth hormone level show for you to discard acromegaly as a diagnostic?
Less than 0.5
