Dexamethasone is frequently used in diagnostic work-up of patients suspected of having Cushing's syndrome. We report the case of a young woman whose cortisol production paradoxically increased following dexamethasone administration. A 27 years old woman presented with intermittent facial rounding (see photos), weight gain (6 kg), hirsuitism, spontaneous bruising, menstrual irregularity. On examination the only feature to suggest Cushing's syndrome was very thin skin on the back of hands. The initial impression was of PCOS because of longstanding menstrual irregularity and hirsuitism but to exclude Cushing's syndrome the following tests were performed. Basal tests: urine free cortisol (UFC) 40; 45; 95 nmol/24h (3 D); plasma cortisol (PC) 160 nmol/l; ACTH <5 ng/l. After overnight 2 mg dexamethasone PC was 331 nmol/l (n=<50). Long dexamethasone suppression test (LDST): 1) after dexamethasone 0.5 mg 6hourly (2 D) UFC was 203 (D 1) and 436 (D 2) nmol/24h, PC (D 2) 486 nmol/l, ACTH <5 ng/l; 2) after dexamethasone 2mg 6 hourly (2 D) UFC 620 nmol/24h, PC 630 nmol/l, ACTH < 5 ng/l. A second LDST was performed with the identical paradoxical increase in UFC and plasma cortisol and suppressed ACTH. Careful re-examination of the patient revealed multiple cutaneous lentigenes. Mother and brother have multiple lentigenes; maternal grandmother had high BP since a young woman providing possible evidence of autosomal dominant inheritance. This suggests that the patient may have Carney Complex with micronodular adrenal hyperplasia. Paradoxical increases in urine cortisol have been reported in such patients in vivo and adrenal tissue from them increases cortisol production in vitro in response to dexamethasone. This diagnosis should be considered in the unusual event of a patient exhibiting an increase in cortisol during LDST.
22 - 24 Mar 2004
British Endocrine Societies