Growth Hormone Adenoma / Acromegaly

Snapshot

• A 52 year-old man complains of increased hat size and headaches when he wakes up in the morning. Physical exam reveals mild diastolic hypertension, prominant jaw with spaces between the teeth, large hands and feet, and generalized muscle weakness.

Introduction

• Benign pituitary adenoma that releases excess growth hormone
  • GH stimulates release of insulin growth-like factor 1 
• Gigantism if the condition occurs before the fusion of the epiphysis
• Acromegaly if it occurs after skeletal epiphyseal closure

Presentation

• Symptoms
  • generalized enlargement of bone and soft tissue
    • large hands and feet
    • frontal bossing
      • leads to increased hat size
    • space between teeth
      • jaw grows but teeth remain the same size
    • macroglossia
    • carpal tunnel syndrome 
      • size of median nerve increases due to edema
• Physical exam
  • HTN
• due to the antinatriuretic action of GH

Evaluation

• Photographic changes
  • for acromegalic features examine an old photograph to reveal changes in facial bones
• Serology 
  • ↑ IGF-1 
    • more sensitive test because the level is more constant than the pulsatile release of GH
  • hyperglycemia
    • due to gluconeogenic action of GH
• Suppression tests
  • GH release not suppressed by glucose challenge
• MRI/CT
  • shows enlargement of sella turcica on imaging
• Cardiomegaly on CXR
• hypertrophy of left ventricle

Treatment

• Surgical
  • transphenoidal surgery
• Medical 
  • octreotide (somatostatin analogue)
    • supresses GH release
  • dopamine analog
    • second line for refractory tumors
  • GH receptor antagonists 
• pegvisomant 

Prognosis, Prevention, and Complications

• Cardiomegaly progressing to CHF is the most common cause of death