Addison's disease in Africa - A teaching hospital experience

OBJECTIVE. Addison's disease may present with diverse and non-specific clinical and biochemical features. Contentious issues include the appropriate criteria for the interpretation of the ACTH stimulation test and the necessary extent of investigation to identify a specific aetiology for the hypoadrenalism. The experience of Addison's disease at a South African teaching hospital was reviewed to (1) record the aetiology and spectrum of presentation, (2) examine the performance of the ACTH stimulation test and (3) determine the utility of adrenal CT scan and biopsy. METHODS. Retrospective study of patients admitted to a South African teaching hospital from 1980 to 1997 with a diagnosis of acute Addison's disease. PATIENTS AND MEASUREMENTS. Fifty patients presenting with acute Addison's disease were identified by a search of hospital records. Pretreatment biochemical and haematological parameters were recorded. The cortisol response at 20 and 60 min to an intravenous injection of 250 μg synacthen (Cortrosyn®) was analyzed. In a subgroup of affected subjects, the bone mineral density (BMD) in the lumbar spine and femoral neck was measured during long-term follow- up. RESULTS. Presenting features included hyperpigmentation (86%), weight loss (67%), abdominal pain (20%) and diarrhoea (16%). Thirty-nine patients (78%) were hyponatraemic, while 26 (53%) were hyperkalaemic. Nine patients (18%) were hypoglycaemic and 21% had hypercalcaemia. The mean basal cortisol was 148 nmol/l (range 10-487) and 16 patients (40%) had a normal basal cortisol. The mean cortisol 20 min after ACTH stimulation was 172 nmol/l (range 19-588). There was no significant increase in serum cortisol following ACTH stimulation (P>0.05). Adrenal CT scans were performed in only 24 patients (48%) and were normal in 10, while abnormalities were detected in 14 patients (bilateral enlargement in 11, calcification in two and atrophic adrenals in one). Eight patients had a DEXA scan performed during follow-up - four were osteopaenic in the lumbar spine and five at the femoral neck. The probable aetiology of Addison's was idiopathic in 42%, related to active TB in 18%, old TB in 16%, autoimmune in 12% and malignancy with metastases in 6% - single cases were due to sarcoid, iron overload and adrenoleukodystrophy. Adrenal biopsy was performed in two patients and was diagnostic of malignancy in both cases. The mortality within the first month after hospitalization was 12%. CONCLUSIONS. In our experience, Addison's disease is frequently idiopathic, presents with protean manifestations and should be considered in patients with unexplained hyperpigmentation or gastrointestinal complaints, particularly when associated with hyponatraemia and hyperkalaemia. A normal basal cortisol does not exclude the diagnosis which requires ACTH stimulation testing.