Examkin

Soru

Zorluk: OrtaEndocrinology and Metabolism

A 39-year-old woman is evaluated for a 1-year history of progressive central obesity, facial plethora, and new-onset hypertension. She also reports menstrual irregularities and easy bruising. Physical examination reveals violaceous striae on her abdomen and prominent proximal muscle weakness in her lower extremities. She does not use any prescription, over-the-counter, or topical medications. Suspecting an endogenous hypercortisolism disorder, her physician decides to initiate a comprehensive diagnostic workup. Arrange the following diagnostic modalities in the correct sequential order for the evaluation of this patient's condition, starting from the initial screening to the definitive localization of the source.

  1. 1Perform a 24-hour urine free cortisol assay, late-night salivary cortisol test, or overnight low-dose dexamethasone suppression test
  2. 2Measure plasma adrenocorticotropic hormone (ACTH) concentration
  3. 3Obtain a magnetic resonance imaging (MRI) scan of the pituitary gland
  4. 4Perform bilateral inferior petrosal sinus sampling (IPSS) for ACTH measurement

Cevap

The correct sequence is to first confirm hypercortisolism with a 24-hour urine free cortisol, late-night salivary cortisol, or low-dose dexamethasone test; second, determine ACTH dependence by measuring plasma ACTH; third, localize the source with a pituitary MRI; and fourth, perform IPSS if the MRI is equivocal or shows a sub-centimeter lesion.
The diagnostic evaluation for Cushing syndrome requires strict adherence to a sequential algorithm to prevent misdiagnosis and avoid unnecessary invasive procedures. The foundational first step is confirming endogenous hypercortisolism using tests such as 24-hour urine free cortisol, late-night salivary cortisol, or a low-dose dexamethasone suppression test. Only after confirmation should a plasma ACTH level be drawn. This second step distinguishes between ACTH-independent (adrenal tumors) and ACTH-dependent (pituitary or ectopic) etiologies. If ACTH is elevated or inappropriately normal, a pituitary MRI is indicated to visualize a potential corticotroph adenoma. Because microadenomas can be too small to be seen on MRI, and because non-functioning incidentalomas are common, bilateral inferior petrosal sinus sampling (IPSS) serves as the definitive final step to prove the pituitary is the source of excess ACTH if the MRI reveals no lesion or a lesion smaller than 6 mm.

Adım Adım Çözüm

1
Confirm the presence of pathological hypercortisolism.
Perform a 24-hour urine free cortisol, late-night salivary cortisol, or overnight low-dose dexamethasone suppression test.
You must establish that the patient actually has excess endogenous cortisol production before attempting to find the anatomical source, as pursuing localization without biochemical confirmation leads to false-positive diagnoses.
2
Determine if the hypercortisolism is ACTH-dependent or ACTH-independent.
Measure the plasma ACTH concentration.
This biochemical step reliably differentiates between an autonomous adrenal source (suppressed ACTH) and a central/ectopic source (elevated or inappropriately normal ACTH).
3
Attempt non-invasive anatomical localization of the ACTH source.
Obtain a pituitary MRI.
Because Cushing disease (pituitary adenoma) is the most common cause of ACTH-dependent hypercortisolism, MRI of the sella turcica is the safest and most appropriate initial imaging modality.
4
Differentiate a pituitary source from an ectopic ACTH-secreting tumor if imaging is indeterminate.
Perform bilateral inferior petrosal sinus sampling (IPSS).
If the MRI is normal or shows an incidentaloma (lesion < 6 mm), IPSS is the gold-standard invasive test to confirm a pituitary source before proceeding to transsphenoidal surgery.

Anahtar Kavram

Diagnostic algorithm for endogenous Cushing syndrome
Bu soruyu puanla

Konular

Endocrinology and Metabolism

Bu konudan daha fazla soru