Acromegaly Flashcards
What produces growth hormone?
Anterior pituitary gland
What cells in the anterior pituitary gland produce growth hormone?
Somatotrophs
What is the most common cause of unregulated growth hormone secretion?
Pituitary adenoma
Rarely, acromegaly can be secondary to a cancer like lung or pancreatic cancer, with a tumour secreting…
ectopic GHRH or GH
What is it called when a secondary tumour produces ectopic GHRH or GH?
Paraneoplastic syndrome
What is a common complication of a pituitary adenoma in acromegaly?
Pressing on the optic chiasm above
B_______ h_____ can be cuased by the pituitary adenoma pressing on the optic chiasm
Bitemporal hemianopia (loss of outer half of vision in both eyes)
What are symptoms of excess growth hormone in acromegaly?
Frontal bossing (prominent forehead and brow)
Coarse, sweaty skin
Large nose
Macroglossia (large tongue)
Large hand and feet
Prognathism (large protruding jaw)
Sleep apnoea
large interdental gaps
What are other features of acromegaly?
Hypertrophic heart
hypertension
T2DM
Carpal tunnel syndrome
Arthritis
Colorectal cancer
Why does acromegaly cause hypertension?
GH promotes vasoconstriction which increases peripheral resistance, elevating bp.
Can also increase renal sodium reabsorption resulting in fluid retention so blood volume increases contributing to hypertension.
Why does acromegaly cause T2 DM?
GH counteract the actions of insulin and promote insulin resistance leading to reduced glucose uptake. Also impairs pancreatic beta cells production of insulin and it promotes gluconeogenesis.
How does acromegaly cause carpal tunnel syndrome?
GH leads to soft tissue growth including enlargement of bones and soft tissue in hands and wrist.
This can reduce the space available within the carpal tunnel, compressing the median nerve. Pain, numbness, tingling and weakness in hands.
How does acromegaly cause arthritis?
GH leads to overgrowth of bones and joints
Arthropathy (joint enlargement) contributes to pain, stiffness and reduced range of motion.
Also increased stress on joints can increase breakdown of cartilage and changes in underlying bone.
how does acromegaly cause colorectal cancer?
GH associated with insulin resistance which may lead to hyperinsulinemia which is potential factor in development of colorectal cancer.
GH can stimulate cell proliferation and inhibit apoptosis
What can be looked for in the blood to help diagnose acromegaly?
Insulin-like growth factor (IFG-1) indicates GH level, however naturally fluctuates throughout day. Produced by liver.
1st line test.
What is the growth hormone suppression test?
Measure GH levels
75g glucose drink consumed.
2 hours later, measure again.
If not suppressed = acromegaly
Impaired glucose tolerance test / oral glucose tolerance test (OGTT) = gold standard
What is another way to diagnose acromegaly due to a pituitary adenoma?
MRI of pituitary
How do you treat acromegaly?
Trans-sphenoidal surgery to remove pituitary tumour.
or remove tumours producing ectopic GH.
Radiotherapy may be used as part of treatment.
What if surgery is not practical?
GH receptor antagonist: pegvisomant, SC injection daily
Somatostatin analogues (block GH release): octreotide
Dopamine agonists (block GH release): bromocriptine
Somatostatin is also known as g_____ h____-i_____ hormone and normally secreted by the brain, GI tract and pancreas
growth hormone-inhibiting hormone
Somatostatin and ____ have inhibitory effects on GH release
dopamine
