Acromegaly Flashcards
1
Q
acromegaly
A
due to increased secretion of growth hormone from a GH secreting pituitary tumour (99%) or hyperplasia
2
Q
GH secretion
A
pulsatile, peaks during sleep
3
Q
effects of GH on growth
A
- GH and IGF-1 stimulates proliferation of chondrocytes resulting in bone growth
- IGF-1 stimulate both the differentiation and proliferation of myoblasts and stimulates amino acid uptake and protein synthesis = muscle growth
- GH stimulates skeletal and soft tissue growth, therefore produce gigantism in children (if acquired before epiphyseal fusion) and acromegaly in adults
4
Q
metabolic effects of GH
A
- GH directly and through IGF-I stimulates osteoblast proliferation and activity, promoting bone formation. It also stimulates osteoclast differentiation and activity, promoting bone resorption. The result is an increase in the overall rate of bone remodelling, with a net effect of bone accumulation.
- Protein metabolism: stimulates protein anabolism
- Fat metabolism: enhances use of fat by stimulating triglyceride breakdown and oxidation in adipocytes
- Carbohydrate metabolism: supresses the abilities of insulin to stimulate uptake of glucose in peripheral tissues and enhance glucose synthesis in the liver. Somewhat paradoxically, administration of growth hormone stimulates insulin secretion, leading to hyperinsulinemia.
5
Q
control of GH secretion
A
- GHRH
- Somatostatin inhibits GH in response to GHRH and other stimulatory factors such as low blood glucose concentration
- Produced from the delta cells of the pancreas, pylorus and duodenum
- Ghrelin (‘hunger hormone’) stimulates GH secretion
- GH secretion is also part of a negative feedback loop involving IGF-1
6
Q
what does increased GH cause in children and adults
A
gigantism in children (if acquired before epiphyseal fusion) and acromegaly in adults.
7
Q
clinical features
A
- giant
- thickened soft tissue - skin, large jaw, sweaty large hands
- hypertension and cardiac failure
- snoring/obstructive sleep apnoea
- headaches
- DM
- local pituitary effects: visual fields and hypopituitarism
8
Q
what is the snoring/OBSA due to
A
enlargement of pharyngeal tissue
9
Q
what are headaches due to
A
- effect of blood vessel swelling (not tumour) and produce a migrainous type headache
- Often relieved immediately by treatment
- can be v severe
10
Q
reason for DM
A
- GH is a stress hormone and causes an increase in BG
- GH supresses the abilities of insulin to stimulate uptake of glucose in peripheral tissues and enhance glucose synthesis in the liver - increased blood glucose
- Somewhat paradoxically, administration of growth hormone stimulates insulin secretion, leading to hyperinsulinemia
11
Q
what is one at risk of
A
early CV death
12
Q
what is there a risk of developing in the colon
A
colonic polyps and colon cancer
13
Q
somatostatin effect on GH
A
may be in reponse to low BG
14
Q
diagnosis
A
- diagnostic: GTT
- IGF-1 - age and sex matched
- visual field
- CT/MRI scan of pituitary fossa
- pituitary function test for other hormones
15
Q
OGTT
A
- BG levels are raised in the patient by giving them a sugary drink after a period of fasting, this should suppress GH levels
- normally, GH suppressed to <0.4ug/L
- in acromegaly GH will be unchanged - this is diagnostic
- dont rely on random GH as secretion is pulsatile and during peaks acromegalic and normal levels overlap
20
Q
somatostatin analogues
A
- Reduce GH in most patients and cause tumour shrinkage (30-50% decrease in size, takes 6-12 months)
- Can be used as an adjunct to surgery: they are used pre-op to rapidly relieve headaches and improve the outcome.
