Hypercortisolaemia without clinical stigmata of Cushing syndrome

A man in his 20s was referred by his general practitioner because of the finding of adrenocorticotropic hormone (ACTH)-dependent hypercortisolaemia, discovered as part of investigation of fatigue and alopecia. The man had no other clinical findings suggestive of Cushing syndrome. Further investigation revealed intact diurnal rhythm in cortisol production, normal bone density and excluded assay interference. Further investigation revealed the man's sibling had been labelled as having Cushing syndrome because of similar biochemical abnormalities. A diagnosis of familial primary generalised glucocorticoid resistance syndrome was made. Testing for mutations in the