acromegaly

Question 1

What is acromegaly?

Answer 1

Acromegaly is the clinical manifestation of excessive growth hormone (GH). Growth hormone is produced by the anterior pituitary gland. The most common cause is unregulated growth hormone secretion by a pituitary adenoma. This adenoma can be microscopic or can be a significantly sized tumour that causes compression of local structures. Rarely, acromegaly can also be secondary to a cancer, such as lung or pancreatic cancer, that secretes ectopic growth hormone releasing hormone (GHRH) or growth hormone.

Question 2

What is a key visual feature of acromegaly?

Answer 2

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 stereotypical “bitemporal hemianopia” visual field defect. This describes loss of vision on the outer half of both eyes

Question 3

How does acromegaly present?

Answer 3

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 4

How is acromegaly treated (tumour)?

Answer 4

Trans-sphenoidal (through the nose and sphenoid bone) surgical removal of the pituitary tumour is the definitive treatment of acromegaly secondary to pituitary adenomas.

Question 5

How is acromegaly caused by ectopic hormones treated?

Answer 5

Where acromegaly is caused by ectopic hormones from a pancreatic or lung cancer, surgical removal of these cancers is the treatment.

There are medication that can be used to block growth hormone

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)
Somatostatin is known as “growth hormone inhibiting hormone”. It is normally secreted by the brain, gastro-intestinal tract and pancreas in response to complex triggers. One of the functions of somatostatin is to block GH release from the pituitary gland. Dopamine also has an inhibitory effect on GH release, however not as potent as somatostatin.