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Zorluk: OrtaOrdering Laboratory Tests

A 47-year-old woman is evaluated in the clinic for an 8-month history of progressive weight gain, profound fatigue, and difficulty climbing stairs. She also reports new-onset facial hair growth and irregular menstrual cycles. Her medical history is otherwise unremarkable, and she explicitly denies taking any prescription medications, over-the-counter supplements, or topical creams. Vital signs show a temperature of 37.1°C (98.8°F), blood pressure of 154/94 mmHg, heart rate of 82/min, and respiratory rate of 14/min. Physical examination reveals central adiposity, facial plethora, a prominent dorsocervical fat pad, and wide, violaceous striae over the lower abdomen. Proximal muscle weakness is noted in both lower extremities. Which of the following is the most appropriate next step in evaluation?

  1. Overnight 1-mg dexamethasone suppression testCevap
  2. B
    Serum adrenocorticotropic hormone (ACTH) concentration
  3. C
    Random morning serum cortisol level
  4. D
    High-dose (8-mg) dexamethasone suppression test
  5. E
    Magnetic resonance imaging (MRI) of the pituitary gland

Cevap

The most appropriate next step is to screen for hypercortisolism using an overnight 1-mg dexamethasone suppression test.
This patient's clinical presentation—featuring progressive weight gain, proximal muscle weakness, wide violaceous striae, facial plethora, and hypertension—is highly suspicious for Cushing syndrome. The first step in evaluating suspected hypercortisolism is to biochemically establish the diagnosis. The accepted first-line screening tests are the overnight 1-mg low-dose dexamethasone suppression test, 24-hour urinary free cortisol measurement, and late-night salivary cortisol assessment. Only after the diagnosis of hypercortisolism is confirmed should the clinician proceed to determine the etiology (e.g., measuring ACTH).

Adım Adım Çözüm

1
Analyze the patient's clinical presentation.
The patient exhibits classic stigmata of Cushing syndrome, including central adiposity, violaceous striae, proximal muscle weakness, hirsutism, and new-onset hypertension.
Recognizing the constellation of signs and symptoms is necessary to form a pre-test clinical suspicion for hypercortisolism.
2
Determine the first step in the diagnostic algorithm for Cushing syndrome.
The initial step must biochemically confirm the presence of excessive cortisol before attempting to identify the source.
Proceeding directly to etiology-specific tests or imaging without confirming the disease can lead to misdiagnosis due to incidental findings or physiologic variations.
3
Select the appropriate laboratory test for initial screening.
The overnight 1-mg low-dose dexamethasone suppression test is selected.
It is one of the three highly sensitive first-line screening modalities (along with 24-hour urinary free cortisol and late-night salivary cortisol) for establishing the diagnosis.

Anahtar Kavram

The initial laboratory evaluation of suspected Cushing syndrome requires confirming hypercortisolism with a 24-hour urinary free cortisol, late-night salivary cortisol, or a low-dose dexamethasone suppression test before evaluating ACTH levels or obtaining imaging.
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