Overview

Acromegaly is a condition resulting from excess growth hormone (GH) after the closure of growth plates, leading to the overgrowth of all organ systems, bones, joints, and soft tissues. Gigantism is where excess GH release occurs before the end of puberty and growth plate closure, leading to excess height.

GH stimulates the production of insulin-like growth factor 1 (IGF-1) which plays an important role in growth.

To help make sense of this chapter, it may be helpful to refer to Endocrine and Metabolic Physiology.

Epidemiology

  • Annual incidence is 1.1/100,000
  • Men and women are equally affected
  • Usually seen in people aged 40-50 years 

Causes

  • Excess GH secretion from a pituitary adenoma – in around 95% of cases
  • Ectopic neuroendocrine tumours (e.g. gastrointestinal tumours)

Presentation

Features due to excess GH/IGF-1

  • Facial changes:
    • Frontal bossing
    • Enlarged nose
    • Prognathism
    • Maxillary widening
    • Macroglossia
  • Skin, soft tissue, and bone:
    • Increased sweating and oily skin
    • Increased skin thickness
    • Increased foot and hand size
    • Osteoarthritis
  • Cardiovascular:
  • Endocrine and metabolic:
    • Impaired glucose tolerance
    • Diabetes mellitus

Features due to prolactin co-secretion

Prolactin co-secretion is seen in 1/3 of patients:

Features due to tumour mass effects

  • Visual field defects – classically a bitemporal hemianopia
  • Headaches
  • Hypopituitarism if other parts of the pituitary gland are compressed

Investigations

  • Serum insulin-like growth factor 1 (IGF-1):
    • This is done as an initial screening test
    • IGF-1 is elevated
  • Oral glucose tolerance test (OGTT) + measure GH:
    • Done after the serum IGF-1 screening test to confirm the diagnosis
    • GH is suppressed after consuming glucose in unaffected patients, in acromegaly, there is a failure of suppression
    • GH is not suppressed to <1 μg/L after the OGTT
  • Pituitary MRI:
    • May demonstrate a pituitary adenoma
    • Some may be missed as they can be very small

Management

  • 1st-line: trans-sphenoidal surgery
  • If surgery is unsuitable/not possible, consider one of the following:
    • Somatostatin analogues (e.g. octreotide):
      • Directly inhibits GH release
      • Used in preference to the other options
    • GH receptor antagonists (e.g. pegvisomant)
    • Dopamine agonists (e.g. bromocriptine)
  • Radiotherapy can be considered if surgery is unsuitable/not possible and medical treatment has failed

Complications

  • Hypertension
  • Hypertrophic cardiomyopathy
  • Arrhythmia
  • Sleep apnoea
  • Osteoarthritis
  • Diabetes mellitus
  • Carpal tunnel syndrome
  • Colorectal cancer

Prognosis

  • Early diagnosis and intervention are associated with a better prognosis
  • The presence of complications is associated with a poorer prognosis

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