Endocrine Abstracts

A case of ectopic ACTH with severe opportunistic infection
ECI Hatfield, S Pal, K Meeran, G Williams, JF Todd.
Endocrine Unit, Imperial College, Hammersmith Hospital, London, UK
A twenty six year old female presented with symptoms and signs suggestive of Cushing's Syndrome. Initial investigations showed hypokalaemia (potassium 2.3nmol/L), elevated urinary free cortisols, (3400, 18,000, 31,000 nmol/24 hour (NR <270)), diabetes (fasting glucose =9 mmol/L), loss of diurnal cortisol rhythm (9am 1846 nmol/L, midnight 1453 nmol/L), and high 9am ACTH (204.5 ng/L). On LDDST, cortisol remained elevated (basal 1846nmol/L, 48hr 1291 nmol/L). On HDDST, cortisol suppressed to below 50% of basal (basal 1472 nmol/L, 48hr 649 nmol/L). An MRI scan showed a bulky pituitary but Inferior Petrosal Sinus Sampling excluded a diagnosis of pituitary driven Cushing's. Urine 5HIAA's were modestly elevated (45, 45, 58 micromol/vol (NR<40)). However, an octreotide scan and CT scan of chest, abdomen and pelvis were normal. Therefore the diagnosis was that of ectopic ACTH, with no primary source localised.
Initial treatment included potassium sparing diuretics, insulin, ketoconazole and metyrapone. However, two weeks later the patient developed Pneumocystis Carinii pneumonia. This responded well to treatment with high dose septrin and methylprednisolone. The patient is currently awaiting bilateral adrenalectomy. She will require long term follow up to identify the source of ectopic ACTH.
Patients with uncontrolled Cushing's syndrome, particularly those with ectopic ACTH, where the cortisol levels may be extreme, are at high risk of bacterial and opportunistic infection. In both this case and another reported case, overwhelming opportunistic infection occurred several days after cortisol-lowering therapy was instigated. Therefore, it has been suggested that in patients with very high cortisol levels, prophylactic treatment for Pneumocystis Carinii infection should be given prior to commencing cortisol-lowering therapy.
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