Article Text
Summary
Cushing's syndrome (CS) can be classified as adrenocorticotropic hormone (ACTH)-dependent or ACTH-independent depending on the ACTH levels. However, 30% of the patients with CS have ACTH levels in the ‘grey zone’ (5–20 pg/mL), thereby posing a challenge in establishing the aetiological diagnosis. In a patient with full-blown features of Cushing's syndrome with equivocal ACTH levels, and a pituitary microadenoma on contrast-enhanced MRI sella, can falsely lead to a diagnosis of Cushing's disease. Pituitary microadenoma, if <6 mm in size, may be an incidental finding (incidentaloma) in this scenario and can be present in ∼3–27% of the healthy population. Therefore, in a patient with CS with equivocal ACTH levels and a pituitary microadenoma, multiple samplings for ACTH and adrenal imaging should be performed to exclude ACTH-independent CS and if required, bilateral inferior petrosal sinus sampling to determine the source of ACTH excess.
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Footnotes
Contributors KDJ wrote the manuscript and managed the patient. RW edited the manuscript. SK performed surgery. AB edited the manuscript and supervised patient management.
Competing interests None declared.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.