A 37-year-old woman presents to the emergency room after falling down some stairs at work. She reports no pre-monitory symptoms prior to the fall or any loss of consciousness. Recently she has noticed persistent symptoms of fatigue, muscle weakness, and unexpected weight gain. She has no past medical history and is not taking any medications.On examination, the blood pressure is 164/92 mm Hg and heart rate is 84/min. There are multiple skin bruises, facial fullness, and truncal obesity with red “stretch marks.” Muscle strength in the proximal muscles is 4/5 and the reflexes are normal. Which of the following is the most appropriate initial diagnostic test?
A 37-year-old woman presents to the emergency room after falling down some stairs at work. She reports no pre-monitory symptoms prior to the fall or any loss of consciousness. Recently she has noticed persistent symptoms of fatigue, muscle weakness, and unexpected weight gain. She has no past medical history and is not taking any medications.On examination, the blood pressure is 164/92 mm Hg and heart rate is 84/min. There are multiple skin bruises, facial fullness, and truncal obesity with red “stretch marks.” Muscle strength in the proximal muscles is 4/5 and the reflexes are normal. Which of the following is the most appropriate initial diagnostic test?
💡 Explanation
## **Core Concept**
The patient's presentation suggests Cushing's syndrome, a condition caused by excess cortisol levels. This can be due to various reasons including exogenous steroid use, ACTH-producing pituitary tumors (Cushing's disease), adrenal tumors, or familial Cushing's syndrome. The clinical features of Cushing's syndrome include weight gain, particularly in the trunk, hypertension, fatigue, muscle weakness, and characteristic skin changes such as striae.
## **Why the Correct Answer is Right**
The most appropriate initial diagnostic test for suspected Cushing's syndrome is the **late-night salivary cortisol test** or **24-hour urine free cortisol**. However, given the options and common practice, measuring **24-hour urine free cortisol (Option C)** is often considered a practical initial step. This test is non-invasive and helps confirm the diagnosis of Cushing's syndrome by assessing the integrated cortisol production over a 24-hour period. Elevated levels suggest excess cortisol production.
## **Why Each Wrong Option is Incorrect**
- **Option A:** While a **complete blood count (CBC)** might be part of a general workup, it is not specific for diagnosing Cushing's syndrome. It could show findings indirectly related (e.g., polycythemia due to hypertension), but it's not diagnostic.
- **Option B:** A **thyroid function test (TFT)** might be useful given the non-specific symptoms like weight gain and fatigue but is not directly related to the diagnosis of Cushing's syndrome.
- **Option D:** Although **plasma ACTH levels** can help in the differential diagnosis of Cushing's syndrome (distinguishing between ACTH-dependent and ACTH-independent causes), it's not typically the initial diagnostic test but rather a follow-up test after confirming hypercortisolism.
## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is to suspect Cushing's syndrome in patients presenting with **central obesity, hypertension, and proximal muscle weakness**. The presence of **striae (stretch marks)**, particularly if purple or red, is highly suggestive. Early recognition and diagnosis are crucial as Cushing's syndrome can lead to significant morbidity if untreated, including diabetes, osteoporosis, and cardiovascular disease.
## **Correct Answer:** C. 24-hour urine free cortisol.
✓ Correct Answer: C. overnight dexamethasone suppression test
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