Acromegaly Flashcards
What is acromegaly?
It is defined as a condition that results from excessive production of growth hormone (GH) after fusion of the epiphyseal plates in bone
What is gigantism?
It is defined as a condition that results from excessive production of growth hormone (GH) before fusion of the epiphyseal plates in bone
What are the four risk factors of acromegaly?
Pituitary Adenoma
Pancreatic Cancer
Lung Cancer
Multiple Endocrine Neoplasia One
What is the most common risk factor of acromegaly?
Pituitary Adenoma
How does pituitary adenoma result in acromegaly?
GH is produced in the anterior pituitary and therefore the formation of an adenoma tumour would result in the unregulated production of this hormone
How does cancer cause acromegaly?
They can result in the production of ectopic GH or GHRH
What are the nine clinical features associated with acromegaly?
Tissue Overgrowth
Frontal Bossing
Macroglossia
Prognathism
Interdental Spaces
Excessive Sweating
Carpal Tunnel Syndrome
Bitemporal Hemianopia
Galactorrhoea
What is frontal bossing?
It is defined as a prominent forehead and brow
What is macroglossia?
It is defined as an increased tongue size
What is proganthism?
It is defined as a protruding jaw
How does acromegaly result in carpal tunnel syndrome?
The enlargement of soft tissue within the wrists causes compression of the nerves within the carpal tunnel
What is bitemporal hemianopia?
It is defined as the loss of vision on the outer half of both eyes
How does acromegaly result in bitemporal hemianopia?
In most cases, acromegaly is associated with pituatary adenomas
Due to the fact that the pituitary gland is situated below the optic chiasm, when tumour formation occurs in this gland it leads to compression of the optic chiasm
How does acromegaly result in galactorrhoea?
In most cases, acromegaly is associated with pituatary adenomas
In some cases, this results in increased prolactin levels
What are the three investigations used to diagnose acromegaly?
Blood Tests
MRI Scan
Visual Field Tests
What two blood tests are used to diagnose acromegaly?
Insulin Growth Factor-1 (IGF-1)
Oral Glucose Tolerance Test + Serial Growth Hormone Levels
When is IGF-1 used to diagnose acromegaly?
It is the first line investigation used to diagnose acromegaly
What IGF-1 result indicates acromegaly?
Increased IGF-1 Levels
How is IGF-1 used to diagnose acromegaly?
Growth hormone results in the production of insulin growth factor-1
There is a negative feedback system, in which increased insulin growth factor-1 levels inhibits the production of growth hormone
In acromegaly, there is loss of this negative feedback inhibition and therefore the body continues to produce growth hormone, regardless of increased insulin growth factor-1 levels
When is the oral glucose tolerance test with serial growth hormone levels used to diagnose acromegaly?
It is the second line investigation used to diagnose acromegaly, which is conducted following a positive IGF-1 test
What oral glucose tolerance test with serial growth hormone result indicates acromegaly?
Hyperglycaemia which is precipitated through the oral glucose tolerance test results in growth hormone levels > 1mu/L
How is an oral glucose tolerance with serial growth hormone levels test used to diagnose acromegaly?
Growth hormone results in the production of glucose
There is a negative feedback system, in which hyperglycaemia inhibits the production of growth hormone – usually suppressing levels to < 1 mu/L
In acromegaly, there is loss of this negative feedback inhibition and therefore the body continues to produce growth hormone, regardless of hyperglycaemia
Why are growth hormone levels not measured to diagnose acromegaly?
Growth hormone levels fluctuate during the day and therefore cannot provide diagnostic information
What are the two electrolyte disturbances associated with acromegaly?
Hypercalcaemia
Hyperphosphotaemia
How are MRI scans used to diagnose acromegaly?
They can be used to identify pituatary adenomas, which is the most common cause of acromegaly
How are visual field tests used to diagnose acromegaly?
They can be used to identify bitemporal hemianopia, which is a complication of pituatary adenomas - most common cause of acromegaly
What are the three pharmacological management options of acromegaly?
Somatostatin Analogues
Dopamine Agonists
Growth Hormone Receptor Antagonists
When are somatostatin analogues used to manage acromegaly?
They are the first line pharmacological option
What is the mechanism of action of somatostatin analogues?
They directly inhibit the release of growth hormone
Name two somatostatin analogues used to manage acromegaly
Octreotide
Lanreotide
What is the mechanism of action of dopamine agonists?
They indirectly inhibit the release of growth hormone
Name a dopamine agonist used to manage acromegaly
Bromocriptine
What is the mechanism of action of growth hormone receptor antagonists?
They prevent dimerization of the growth hormone receptor
Name a growth hormone receptor antagonist used to manage acromegaly
Pegvisomant
What is the surgical management option of acromegaly?
Transsphenoidal Surgery
When is transsphenoidal surgery used to manage acromegaly?
It is the first line management option
What is transsphenoidal surgery?
It involves removal of the pituitary adenoma through the sphenoid sinus
What are the six complications associated with acromegaly?
Hypertension
Type Two Diabetes Mellitus
Cardiomyopathy
Colorectal Cancer
Osteoarthritis
Sleep Apnoea
