Clinical Case Study: The Case of the Persistent Fatigue
Patient Profile:
Name: Elena, 38 years old.
Occupation: High school teacher.
Chief Complaint: Progressive weight gain in the midsection, severe fatigue, and "muscle weakness" when climbing stairs.
History of Present Illness:
Over the last 8 months, Elena has gained 25 lbs, despite no changes in her diet or exercise. She notes that while her stomach and face have become "rounder," her arms and legs seem thinner. She has developed dark purple streaks on her abdomen and has been diagnosed with New-Onset Type 2 Diabetes and Hypertension by her primary care physician.
Physical Exam Findings:
Vitals: BP 155/95 mmHg (Hypertensive).
General: "Moon face" (facial rounding) and a "buffalo hump" (fat pad) on the upper back.
Integumentary: Thin, fragile skin with several bruises on the forearms and 1.5 cm wide violaceous striae on the abdomen.
Musculoskeletal: 3/5 strength in proximal hip flexors; patient struggles to stand from a squatting position.
Part 1: Initial Assessment (Guided Questions)
Symptom Mapping: List three clinical findings in Elena’s case that are highly discriminatory for Cushing’s Syndrome versus simple obesity. Why are these specific signs more concerning than just weight gain?
Physiological Connection: Elena has "thin limbs" but a "large trunk." Based on what you know about cortisol's role in protein catabolism (breakdown), explain why her muscles are wasting while her fat is redistributing.
The Diabetes Link: Cortisol is a glucocorticoid. Explain the biochemical mechanism of how chronically high cortisol levels led to Elena's diagnosis of Type 2 Diabetes.
Part 2: Diagnostic Reasoning
Elena’s doctor suspects hypercortisolism and orders a 24-hour urinary free cortisol test and a late-night salivary cortisol test.
Circadian Rhythm: Why is the late-night salivary test specifically useful? What result would you expect to see in a healthy person at 11:00 PM versus a patient with Cushing’s?
Feedback Loop Failure: Elena undergoes a 1 mg Dexamethasone Suppression Test. Her 8:00 AM cortisol level returns at 12.0 µg/dL (Normal suppression is < 1.8 µg/dL).
Does this result indicate that her HPA axis is functioning correctly?
What part of the "negative feedback loop" is failing here?
Part 3: Differential Diagnosis & Conclusion
The "Pseudo-Cushing's" Check: If Elena mentioned she was currently suffering from severe clinical depression or chronic alcoholism, how might that complicate her test results?
Final Hypothesis: Given the proximal muscle weakness and the failure to suppress cortisol with dexamethasone, provide a summary of your suspected diagnosis. What would be the next logical step to find the source of the cortisol (e.g., imaging the head or the abdomen)?
Instructor's Note (For your grading key):
Proximal Weakness: Is the "smoking gun" for Cushing's. It's rare in PCOS or simple obesity.
Striae: Must be $>1\text{ cm}$ and purple; pale striae are common in pregnancy or rapid weight gain.
HPA Axis: In this case, the failure to suppress with Dexamethasone suggests the body is ignoring the "stop" signal, indicating an autonomous tumor (either in the pituitary or adrenal gland).
