A 34-year-old nulliparous woman is evaluated for a 15-kg (33-lb) weight gain over the past eight months. She also reports new-onset facial hair growth and severe proximal muscle weakness that makes climbing stairs difficult. Vital signs show a blood pressure of 158/96 mm Hg. Physical examination reveals central adiposity, violaceous abdominal striae, and facial plethora. She takes no medications and has no history of exogenous glucocorticoid use. Arrange the following diagnostic steps in the most appropriate chronological order for the workup of this patient's condition.
- 1Measurement of late-night salivary cortisol
- 2Measurement of plasma adrenocorticotropic hormone (ACTH)
- 3Magnetic resonance imaging (MRI) of the pituitary gland
- 4Inferior petrosal sinus sampling (IPSS)
Cevap
The correct sequence is to first confirm hypercortisolism (Measurement of late-night salivary cortisol), then determine ACTH dependence (Measurement of plasma ACTH), followed by initial localization (MRI of the pituitary gland), and finally invasive confirmation if imaging is equivocal (Inferior petrosal sinus sampling).
The correct sequence for evaluating suspected Cushing syndrome follows a strict tiered approach to avoid false positives. The first step is to definitively confirm the presence of pathological hypercortisolism with a screening test such as late-night salivary cortisol. Once hypercortisolism is established, the second step is to measure plasma ACTH to determine if the condition is ACTH-dependent or independent. For ACTH-dependent disease, the third step is an MRI of the pituitary gland to look for an adenoma. Finally, if the MRI is negative or shows a lesion smaller than 6 mm, the fourth step is inferior petrosal sinus sampling (IPSS) to confidently differentiate between a pituitary and ectopic ACTH source.
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Test Sequencing in Cushing Syndrome Workup
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