Acromegaly

• Acromegaly


  The result of excessive growth hormone (GH)
• Pathophysiology of Acromegaly


  Growth hormone is produced by the anterior pituitary gland. The most common cause of unregulated growth hormone secretion is a pituitary adenoma, which can be microscopic or a significantly sized tumour that causes compression of local structures. Rarely, acromegaly can also be secondary to cancer, such as lung or pancreatic cancer, with a tumour that secretes ectopic growth hormone-releasing hormone (GHRH) or growth hormone (GH). This is a paraneoplastic syndrome, meaning that it occurs alongside the neoplasm (tumour)
• The optic chiasm sits just above the pituitary gland
• The optic chiasm is where the optic nerves from the eyes cross over to the opposite side of the head before traveling to the visual cortex in the occipital lobe
• A pituitary tumour of sufficient size can press on the optic chiasm, leading to a stereotypical bitemporal hemianopia visual field defect
• Visual field defect in Acromegaly

  Bitemporal hemianopia: loss of the outer half of the vision in both eyes, while the inner half of the vision is spared
• Acromegaly Presentation


  A space-occupying pituitary tumour can cause headaches, visual field defect (bitemporal hemianopia), and excess growth hormone leading to tissue growth like prominent forehead and brow (frontal bossing), coarse, sweaty skin, large nose, large tongue (macroglossia), large hands and feet, large protruding jaw (prognathism). Additional features include hypertrophic heart, hypertension, type 2 diabetes, carpal tunnel syndrome, arthritis, and colorectal cancer
• Link between bilateral carpal tunnel syndrome and acromegaly is significant for the PACES exam
• Link between bilateral carpal tunnel syndrome and acromegaly

  • Presented in PACES exam multiple times
  • Patient presents with symptoms of bilateral carpal tunnel syndrome
  • Diagnosis of carpal tunnel syndrome and identification of underlying cause
• Insulin-like growth factor-1 (IGF-1) testing

  1. Tested on a blood sample

  2. Indicates growth hormone level

  3. Raised in acromegaly
• Growth hormone suppression test

  1. Involves consuming a 75g glucose drink

  2. Growth hormone tested at baseline and 2 hours following the drink

  3. Glucose should suppress the growth hormone level

  4. Failure to suppress indicates acromegaly
• MRI of the pituitary


  1. Used to diagnose pituitary adenoma

  2. May be too small to see on the scan
• Trans-sphenoidal surgery


  1. Definitive treatment for acromegaly secondary to pituitary adenomas

  2. Involves removal of the pituitary tumour through the nose and sphenoid bone
• Treatment for acromegaly caused by ectopic hormones

  1. Surgical removal of tumours ideally

  2. Radiotherapy may be used
• Medical options for reducing growth hormone

  1. Pegvisomant: growth hormone receptor antagonist given by subcutaneous injection

  2. Somatostatin analogues (e.g., octreotide): block growth hormone release

  3. Dopamine agonists (e.g., bromocriptine): block growth hormone release
• Somatostatin


  • Also known as growth hormone-inhibiting hormone
  • Secreted by the brain, gastro-intestinal tract, and pancreas
  • Blocks growth hormone release from the pituitary gland
• Dopamine


  • Has an inhibitory effect on GH release
  • Weaker than somatostatin