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Factitious C ushing's syndrome masquerading as C ushing's disease
Author(s) -
Thynne Tilenka,
White Graham H.,
Burt Morton G.
Publication year - 2014
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/cen.12343
Subject(s) - medicine , endocrinology , urinary system , metyrapone , morning , cushing syndrome , adrenocorticotropic hormone , cushing's disease , prednisolone , hydrocortisone , glucocorticoid , hormone , disease
Summary Context Factitious Cushing's syndrome is extremely rare. The diagnosis is challenging as cross‐reactivity of synthetic corticosteroids or their metabolites in immunoassay measurements of plasma or urinary cortisol can make distinguishing between true and factitious C ushing's syndrome difficult. Adrenocorticotropin ( ACTH ) is usually suppressed in factitious C ushing's syndrome. Patient A 54‐year‐old woman presented with clinical and biochemical features of C ushing's syndrome and an unsuppressed ACTH concentration. She denied recent exogenous corticosteroid use. Investigations and results Initial investigations revealed a markedly elevated urinary free cortisol, mildly elevated midnight salivary cortisol and normal morning cortisol concentration. Plasma ACTH was not suppressed at 13 ng/l ( RR 10–60 ng/l). A pituitary MRI was normal, but inferior petrosal sinus sampling ( IPSS ) revealed a post corticotrophin releasing hormone ACTH ratio >20:1 in the left petrosal sinus. Ketoconazole therapy amplified discordance between the urinary free and morning plasma cortisol concentrations. Further investigation of this discordance using high‐pressure liquid chromatography tandem mass spectrometry ( HPLC ‐ MS / MS ) revealed a urinary free cortisol excretion of only 20 nmol/24 h, but prednisolone excretion of 16 200 nmol/24 h. Conclusions Factitious Cushing's syndrome can mimic endogenous ACTH ‐dependent hypercortisolism during initial investigations and IPSS . This case highlights the importance of (i) recognizing the significance of discordant results; (ii) using an ACTH assay capable of reliably differentiating ACTH ‐dependent from ACTH ‐independent Cushing's syndrome; and (iii) appreciating that IPSS is only useful to localize the source of ACTH in confirmed ACTH ‐dependent Cushing's syndrome. In this case, measurement of corticosteroids by HPLC ‐ MS / MS was essential in reaching the correct diagnosis.