Acromegaly

Question 1

What is acromegaly?

Answer 1

Acromegaly is the clinical manifestation of excessive growth hormone.

Question 2

What is the most common cause of acromegaly?

Answer 2

Unregulated growth hormone secretion by a pituitary adenoma

Question 3

What is a rarer cause of acromegaly?

Answer 3

Acromegaly can be secondary to a cancer, such as lung or pancreatic cancer, that secretes ectopic growth hormone releasing hormone (GHRH) or growth hormone.

Question 4

How does a visual field defect develop in acromegaly?

Answer 4

The optic chiasm sits just above the pituitary gland. The optic chiasm is the point where the optic nerves coming from the eyes crossover to different sides of the head. A pituitary tumour of sufficient size will start to press on the optic chiasm. Pressure on the optic chiasm will lead to a bitemporal hemianopia.

Question 5

Describe how acromegaly presents

Answer 5

Space Occupying Lesion:
Headaches
Visual field defect (“bitemporal hemianopia”)

Overgrowth of tissues:
Prominent forehead and brow (“frontal bossing”)
Large nose
Large tongue (“macroglossia”)
Large hands and feet
Large protruding jaw (”prognathism”)
Arthritis from imbalanced growth of joints

GH can cause organ dysfunction:
Hypertrophic heart
Hypertension
Type 2 diabetes
Colorectal cancer

Symptoms suggesting active raised growth hormone
Development of new skin tags
Profuse sweating

Question 6

What investigations can be done in acromegaly?

Answer 6

A random growth hormone level is not helpful as it will fluctuate, giving false positives and false negatives.
Insulin-like Growth Factor 1 (IGF-1) is the initial screening test (raised)
Oral glucose tolerance test whilst measuring growth hormone (high glucose normally suppresses growth hormone)
MRI brain for the pituitary tumour
Refer to ophthalmology for formal visual field testing

Question 7

How is acromegaly treated?

Answer 7

Medication to block GH:
Pegvisomant (GH antagonist given subcutaneously and daily)
Somatostatin analogues to block GH release (e.g. ocreotide)
Dopamine agonists to block GH release (e.g. bromocriptine)
Treat the cause:
Trans-sphenoidal surgical removal of the pituitary tumour.
Surgical removal of pancreatic or lung cancer.