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Zorluk: ZorDiagnostic Workup and Test Sequencing

During an outpatient endocrine evaluation, a physician evaluates a patient suffering from new-onset, treatment-resistant hypertension, marked proximal myopathy, and progressive truncal adiposity. The patient exhibits classic cutaneous findings, including facial plethora and broad, violaceous abdominal striae. Recent laboratory work definitively established a diagnosis of endogenous hypercortisolism via two distinct, abnormal screening tests: a markedly elevated late-night salivary cortisol and an unsuppressed morning cortisol following a 1-mg overnight dexamethasone suppression test. To elucidate the underlying etiology of this patient's hypercortisolism, which of the following investigations is the most appropriate next step in the diagnostic sequence?

  1. Measurement of plasma adrenocorticotropic hormoneCevap
  2. B
    Magnetic resonance imaging of the pituitary gland
  3. C
    High-dose (8-mg) dexamethasone suppression test
  4. D
    Computed tomography of the adrenal glands
  5. E
    Inferior petrosal sinus sampling

Cevap

Measurement of plasma adrenocorticotropic hormone
Once endogenous hypercortisolism (Cushing syndrome) is confirmed with at least two abnormal first-line tests (such as late-night salivary cortisol, 24-hour urine free cortisol, or 1-mg overnight dexamethasone suppression test), the strict next step in the diagnostic sequence is to measure a plasma adrenocorticotropic hormone (ACTH) level. This crucial biochemical step differentiates ACTH-dependent causes (e.g., pituitary adenoma, ectopic ACTH production) from ACTH-independent causes (e.g., adrenal adenoma or carcinoma). Performing anatomical imaging or further dynamic endocrine testing before this basic biochemical categorization can lead to unnecessary, misdirected, or invasive procedures due to the high prevalence of incidentalomas.

Adım Adım Çözüm

1
Evaluate the current diagnostic status of the patient based on the clinical vignette.
The patient has established endogenous Cushing syndrome based on two concordant, abnormal first-line screening tests (elevated salivary cortisol and abnormal 1-mg overnight dexamethasone suppression test).
Before pursuing etiology, the presence of hypercortisolism must be biochemically confirmed to avoid chasing false positives.
2
Determine the required diagnostic sequence for identifying the etiology of confirmed hypercortisolism.
The algorithm dictates that biochemical localization must precede anatomical localization.
Incidentalomas (both pituitary and adrenal) are common in the general population. Imaging without biochemical guidance often leads to false attribution of the disease source.
3
Select the specific biochemical test that categorizes the hypercortisolism.
Plasma adrenocorticotropic hormone (ACTH) measurement is selected.
An ACTH level robustly separates ACTH-dependent causes (normal or elevated ACTH) from ACTH-independent causes (suppressed ACTH), dictating whether pituitary or adrenal imaging is subsequently appropriate.

Anahtar Kavram

Diagnostic sequencing for Cushing syndrome etiology
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Diagnostic Workup and Test Sequencing

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