Pituitary Disease and Insulinoma

Question 1

What are the clinical features of acromegaly?

Answer 1

• 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 2

How is acromegaly diagnosed and treated?

Answer 2

• Diagnosis
  
  • 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
• Management
  
  • Trans-sphenoidal (through the nose and sphenoid bone) surgical removal of the pituitary tumour is the definitive treatment of acromegaly secondary to pituitary adenomas.
  • Where acromegaly is caused by ectopic hormones from a pancreatic or lung cancer, surgical removal of these cancers is the treatment.
    
    • Pegvisomant (GH antagonist)
    • Somatostatin analogues to block GH release (i.e. ocreotide)
    • Dopamine agonists to block GH release (i.e. 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.

Question 3

What are the causes of hyperprolactinaemia?

Answer 3

• Prolactinoma
• Physiological (lactation/pregnancy)
• Drugs that block dopamine
• ‘Stalk’ effect (loss in inhibitory dopamine by something blocking connection from hypothalamus)

Question 4

How is hyperprolactinaemia diagnosed and treated?

Answer 4

• Diagnosis invovles serum prolactin (usually >6000), MRI and tests for other pituitary function
• Treatment involves dopamine agonists and possibly surgery

Question 5

How is Cushing’s disease diagnosed and treated?

Answer 5

• Diagnosis involves dexamethasone suppression testing
• Treatment is surgery or medical therapy (ketoconazole/metyrapone)

Question 6

What are the features of diabetes insipidus?

Answer 6

• Polydypsia and polyuria (output >3L/day)
• Diagnosis involves stimulating ADH release with water deprivation test
• Treatment involves treating underlying cause and DDAVP

Question 7

What needs to be replaced in panhypopituitarism?

Answer 7

• ACTH - hydrocortisone
• TSH - thyroxine
• FSH/LH - testosterone (males) or oestrogen (females)
• GH - growth hormone
• PRL - no replacement