A 25-year-old female with systemic lupus erythematosus presents with weight gain, moon facies, buffalo hump, and hirsutism. Which of the following is the most appropriate investigation to confirm the diagnosis?

1. A

   Serum ACTH and low-dose dexamethasone suppression test

2. B

   Low-dose dexamethasone suppression test

3. C

   High-dose dexamethasone suppression test

4. D

   Serum ACTH and cortisol levels

Appeared in: INI-CET EXAM -2025

Explanation

• The patient's history of SLE strongly suggests treatment with exogenous corticosteroids, leading to iatrogenic Cushing's syndrome.
• In iatrogenic Cushing's, the external steroids suppress the hypothalamic-pituitary-adrenal (HPA) axis.
• This suppression results in low production of the body's own ACTH from the pituitary and, consequently, low production of endogenous cortisol from the adrenal glands.
• Measuring serum ACTH and cortisol levels directly assesses the status of the HPA axis. Finding low levels of both hormones confirms the diagnosis of iatrogenic Cushing's syndrome.

Why Other Options Were Wrong

• Option A: The low-dose dexamethasone suppression test (LDDST) is a screening tool for endogenous Cushing's syndrome, not iatrogenic. In this case, the patient's HPA axis is already suppressed by external steroids, making this test redundant and less direct.
• Option B: Similar to the combined test, the LDDST alone is used to screen for endogenous Cushing's syndrome by seeing if an external steroid (dexamethasone) can suppress the body's cortisol production. It is not the primary test when an iatrogenic cause is highly suspected.
• Option C: The high-dose dexamethasone suppression test is not a screening or primary diagnostic test. It is used to differentiate the cause of confirmed ACTH-dependent endogenous Cushing's syndrome (i.e., to distinguish between a pituitary adenoma and an ectopic ACTH-producing tumor).

Related Visual

Clinical Relevance

• Nursing practice connection: Use the key finding related to Diagnostic investigation for iatrogenic Cushing's syndrome to guide bedside assessment, documentation, and the next nursing action.
• A thorough medication history is one of the most critical nursing assessments, as it can often reveal the cause of a patient's symptoms, as in this case of iatrogenic Cushing's syndrome.
• Patient education is vital for individuals on long-term steroid therapy. Nurses must teach patients to recognize the signs of Cushing's syndrome and to never stop their medication abruptly to avoid an adrenal crisis.
• What if? If the patient had the same symptoms but no history of SLE or steroid use, the most appropriate initial test would be the low-dose dexamethasone suppression test or a 24-hour urinary free cortisol measurement to screen for endogenous Cushing's syndrome.

How to Approach the Question

• First, identify the cluster of symptoms (weight gain, moon facies, buffalo hump) as the classic presentation of Cushing's syndrome (hypercortisolism).
• Next, analyze the patient's medical history. The diagnosis of SLE is a significant clue.
• Connect the medical history to the symptoms. Recall that autoimmune diseases like SLE are often treated with long-term corticosteroids.
• Formulate a primary hypothesis: The patient has iatrogenic (medication-induced) Cushing's syndrome.
• Based on this hypothesis, determine the expected physiological state: exogenous steroids suppress the body's own HPA axis, leading to low ACTH and low endogenous cortisol.
• Evaluate the given options. Select the test that directly measures the status of the HPA axis, which is the measurement of serum ACTH and cortisol levels.

Concept Tested & Keywords

• Concept Tested: Diagnostic investigation for iatrogenic Cushing's syndrome.
• Stem keywords: systemic lupus erythematosus, weight gain, moon facies, buffalo hump, hirsutism
• Lead-in keywords: most appropriate investigation
• Clinical cues: The patient's history of SLE is a strong indicator for long-term corticosteroid use, pointing towards an iatrogenic cause for the Cushing's symptoms.

Question ID

QNKIspxQEU-IyjAGXC4iyB

Copy ID

Reference Book

E6 Medicine Harrison 22e Part 2 p. 915-917

E6 Ghai Essential Pediatrics(pp 26-904 of 913) p. 545-547

E6 Nelson Textbook of Pediatrics(2024) — Volume 2 p. 1283-1285