Epidemiology
- Incidence: 1.00 cases per 100,000 person-years
- Peak incidence: 30-40 years
- Sex ratio: more common in females 2:1
<1 | 1-5 | 6+ | 16+ | 30+ | 40+ | 50+ | 60+ | 70+ | 80+ |
Pathophysiology
Other causes of hypoadrenalism
Primary causes
- tuberculosis
- metastases (e.g. bronchial carcinoma)
- meningococcal septicaemia (Waterhouse-Friderichsen syndrome)
- HIV
- antiphospholipid syndrome
Secondary causes
- pituitary disorders (e.g. tumours, irradiation, infiltration)
Exogenous glucocorticoid therapy
Clinical features
- lethargy, weakness, anorexia, nausea & vomiting, weight loss, 'salt-craving'
- hyperpigmentation (especially palmar creases), vitiligo, loss of pubic hair in women, hypotension, hypoglycaemia
- hyponatraemia and hyperkalaemia may be seen
- crisis: collapse, shock, pyrexia
Investigations
If an ACTH stimulation test is not readily available (e.g. in primary care) then sending a 9 am serum cortisol can be useful:
- > 500 nmol/l makes Addison's very unlikely
- < 100 nmol/l is definitely abnormal
- 100-500 nmol/l should prompt a ACTH stimulation test to be performed
Associated electrolyte abnormalities are seen in around one-third of undiagnosed patients:
- hyperkalaemia
- hyponatraemia
- hypoglycaemia
- metabolic acidosis
Management
This usually means that patients take a combination of:
- hydrocortisone: usually given in 2 or 3 divided doses. Patients typically require 20-30 mg per day, with the majority given in the morning dose
- fludrocortisone
Patient education is important:
- emphasise the importance of not missing glucocorticoid doses
- consider MedicAlert bracelets and steroid cards
- discuss how to adjust the glucocorticoid dose during an intercurrent illness (see below)
Management of intercurrent illness
- in simple terms the glucocorticoid dose should be doubled
- the Addison's Clinical Advisory Panel have produced guidelines detailing particular scenarios