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Adrenal insufficiency

Corticosteroids

  • Glucocorticosteriods produced in zona fasiculata in supra-renal gland
  • Circadian variation.
  • Adrenocorticotropic hormone (ACTH) also has melanin releasing hormone (MRH) which may cause pigmentation at higher levels.
  • ACTH is stimulated by CRH (Corticotropin-releasing hormone ) and ADH (anti diuretic hormone)

Basal Levels

  • Released episodically and to stress response
  • Basal levels should be taken between 8-9am
  • Suppression and stimulation tests used for diagnosis of deficiency/excess
Dexamethasone suppression tests  
  • inhibit ACTH/CRH release > decrease cortisol levels
  • diagnosis for Cushings

ACTH stimulation test

  • synthetic ACTH to stimulate cortisol production
  • short and 9am stimulation tests are used to differentially diagnosis Addison’s disease from other adrenal insufficiency disorders

Addisons disease – primary hypoadrenalism

  • destruction of entire adrenal cortex (all 3 hormones reduced)
  • differs from pituitary insufficiency as mineralocorticoid levels are normal
  • reduced cortisol levels lead to higher levels of CRH/ACTH
Etiology
  • autoimmune (AI), TB, HIV, surgery, infarction, malignancy, amyloidosis
  • associated w/    Other AI diseases
  • auto-antibodies against 21a hydroxlase

Clinical features

  • vague and non-specific
  • Addison crisis – hypotension and dehydration after illness/surgery ( treatment urgent )
  • Grey pigmentation in majority of cases (increase in ACTH)
  • Postural systolic hypotension (mineralocorticoid deficiency)

Diagnosis

  • If suspected take blood samples and treat urgently (saline/hydrocortisone)
  • Short ACTH stimulation test
    • Impaired cortisol response confirms hypoadrenalism but doesn’t differentiate between Addisons and secondary.
  • 9am plasma ACTH levels
    • ACTH >80ng/l with low cortisol confirms Addisons
  • hyponatremia, hyperkalemia, hypoglycaemia, auto-antibodies

Treatment

  • Treatment regime
  • fludrocortisone treatment assessed by salt balance, no postural blood pressure drop and renin suppression
  • Treat hyperkalemia if necessary
Complications of steroid therapy

Secondary hypoadrenalism

  • hypothalamic-pituitary disease, long term corticosteroid therapy
  • Panhypopituitarism is seen in hypothalamic-pituitary disease,
    • Hydrocortisone should be given before thyroid medication.

Congenital adrenal hyperplasia

  • Autosomal recessive disease, 21-hydroxylase defect (CYP21A2)
  • Lack of cortisol causes an increase in ACTH > hyperplasia of adrenal glands
  • Build-up of steroid precursors lead to androgen pathways > virilisation
  • Clinical features
    • Sexual ambiguity, adrenal failure, salt loss, urogenital abnormalities
    • Later – precocious puberty, hirsuitism
  • Diagnosis
    • Serum 17-hydroxyprogesterone – high levels in blood test is diagnostic of classic 21-hydroxylase deficiency
  • Treatment
    • Dependent upon clinical features and severity
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