Should cortisol levels be routinely checked in patients with obesity?

Cortisol Testing in Obesity: Not Recommended for Routine Screening

Cortisol levels should not be routinely checked in patients with obesity unless there are specific clinical features suggesting Cushing's syndrome, such as unexplained weight gain combined with decreasing height or growth velocity in children, or other specific signs of hypercortisolism. 1, 2

When to Consider Cortisol Testing in Obesity

Cortisol testing should be considered only in specific circumstances:

In Children and Adolescents

• Only test when weight gain is inexplicable AND combined with either:
  • Decreasing height standard deviation score (SDS)
  • Decreasing height velocity 1
• This combination of features has high sensitivity and specificity for Cushing's syndrome in pediatric patients

In Adults

• Consider testing only when clinical features suggest Cushing's syndrome:
  • Central obesity with thin extremities
  • Facial plethora (redness)
  • Proximal muscle weakness
  • Wide purple striae
  • Easy bruising
  • Unexplained osteoporosis 1, 2

Rationale Against Routine Testing

1. Low Prevalence: Cushing's syndrome is rare, with an incidence of approximately 0.5 new patients per million individuals per year in children 1

2. Poor Diagnostic Yield: Very few patients with obesity actually have Cushing's syndrome 1

3. False Positives: Several conditions common in obesity can cause false-positive results:

   • Severe obesity itself
   • Uncontrolled diabetes
   • Depression
   • Alcoholism
   • Medications that alter cortisol metabolism 2

4. Complex Relationship: The relationship between obesity and cortisol is complex:

   • Obese individuals may have altered cortisol metabolism rather than increased production 3, 4
   • Some studies show lower basal cortisol levels in obesity 4, 5
   • Gender differences exist in cortisol metabolism in obesity 6

If Testing is Warranted

When clinical suspicion is present, the Endocrine Society recommends:

1. First-line screening tests:

   • 24-hour urinary free cortisol (UFC)
   • Late-night salivary cortisol (LNSC)
   • Overnight 1-mg dexamethasone suppression test (DST) 2

2. Test selection considerations:

   • For shift workers or those with disrupted circadian rhythm: DST is preferred
   • For monitoring cyclic Cushing's syndrome: LNSC is preferred 2

3. Interpretation:

   • Low clinical suspicion: One abnormal test warrants further evaluation
   • Intermediate to high clinical suspicion: 2-3 screening tests recommended 2

Adrenal Incidentalomas

For patients with adrenal incidentalomas found on imaging:

• Hormone screening including cortisol is recommended regardless of whether the lesion appears benign or malignant 1
• Subclinical Cushing's syndrome is the most common hormonal dysfunction caused by adrenal incidentalomas 1

Common Pitfalls

1. Overdiagnosis: Testing cortisol in all obese patients will lead to many false positives and unnecessary additional testing

2. Misinterpretation: Cortisol metabolism is altered in obesity, which can complicate interpretation of results 3, 6

3. Inadequate follow-up: If initial screening is abnormal, confirmation with additional testing is essential before making a diagnosis 2

4. Failure to recognize pseudo-Cushing's states: Conditions like depression, alcoholism, and poorly controlled diabetes can cause hypercortisolism that resolves when the underlying condition is treated 1

In conclusion, while the relationship between cortisol and obesity is complex, routine screening for cortisol abnormalities in all patients with obesity is not recommended. Testing should be reserved for those with specific clinical features suggesting Cushing's syndrome.