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Addison's Disease

Clinical Features

  • Fatigue, weakness, tiredness
  • Weight loss
  • Dizziness and postural hypotension
  • Joint and muscle pains
  • Gastrointestinal symptoms eg anorexia, nausea, diarrhoea, abdominal cramps
  • Hyperpigmentation (general, palmar creases, pressure areas, scars, buccal)
  • Postural hypotension
  • Associated vitiligo, goitre

    INVESTIGATIONS

    1. Full blood count Mild normocytic anaemia, eosinophilia, lymphoctosis
    2. Urea and electrolytes Mild hyperkalaemia, hyponatraemia, raised urea
    3. 0900h serum cortisol Serum cortisol levels of <70nmol/L is diagnostic of adrenal insufficiency.
    Serum cortisol level of >550nmol/L indicates normal adrenal function.
    Serum cortisol levels between those values require further evaluation.
    Remember that oestrogen therapy increases total cortisol levels by increasing cortisol binding globulin, so ideally, it should be stopped at least 6 weeks prior to testing.

    NB If Addison's disease is suspected clinically or biochemically, please refer to the Endocrine team.

    Hospital investigations

    Synacthen test (0900-1000h) In patients with adrenal insufficiency, peak cortisol levels do not reach 550nmol/L and are often undetectable by the time the patient is symptomatic.
    ACTH x2 Plasma ACTH levels are markedly elevated in primary adrenal insufficiency.
    Adrenal cortex antibodies Antibodies against the adrenal cortex are found in 60-90% of patients with autoimmune adrenal disease.
    Also check thyroid and intrinsic factor autoantibodies.
    TSH, fT4 Check only once adrenal insufficiency has been rectified

    Note: 50% of patients with Addison's disease have another autoimmune endocrine disease and should therefore be screened for thyroid dysfunction and type1 DM.