How to manage a patient with partial adrenal axis responsiveness, as shown by an Adrenocorticotropic hormone (ACTH) stimulation test?

Management of Partial Adrenal Axis Responsiveness

The patient's ACTH stimulation test results indicate partial adrenal insufficiency requiring physiologic glucocorticoid replacement therapy with hydrocortisone 15-20 mg daily in divided doses, along with stress dosing education and medical alert identification. 1

Interpretation of ACTH Stimulation Test Results

The patient's ACTH stimulation test shows:

• Baseline cortisol: 8.4 μg/dL
• 30-minute cortisol: 33.2 μg/dL
• 60-minute cortisol: 37.4 μg/dL

These results demonstrate a suboptimal cortisol response to ACTH stimulation. According to guidelines, a peak cortisol <18 μg/dL (500 nmol/L) is diagnostic of adrenal insufficiency 1. While the patient's peak response exceeds this threshold, the baseline level is concerning, suggesting partial or developing adrenal insufficiency.

Diagnostic Assessment

1. Determine the type of adrenal insufficiency:

   • Measure morning ACTH and cortisol levels to differentiate between primary and secondary adrenal insufficiency
   • Low ACTH with low cortisol suggests secondary adrenal insufficiency
   • High ACTH with low cortisol suggests primary adrenal insufficiency 1

2. Additional testing:

   • Thyroid function tests (TSH and free T4)
   • Gonadal hormones (LH, FSH, testosterone/estradiol)
   • Consider pituitary MRI if secondary adrenal insufficiency is suspected 1

Treatment Algorithm

1. Initiate glucocorticoid replacement:

   • Hydrocortisone 15-20 mg daily in divided doses (typically 10-15 mg in morning, 5 mg in afternoon) 1
   • Alternative: Prednisone 5 mg daily 1

2. Stress dosing education:

   • Minor stress (mild fever, minor illness): Double daily dose for duration of illness
   • Moderate stress (moderate illness, dental procedures): Triple oral dose or hydrocortisone 50-100 mg IM
   • Major stress (surgery, severe illness): Hydrocortisone 100 mg IV/IM every 6-8 hours 1

3. Patient safety measures:

   • Provide medical alert bracelet/card identifying steroid dependence
   • Educate on emergency injection techniques
   • Explain symptoms requiring immediate medical attention 1

Monitoring and Follow-up

1. Regular assessment:

   • Blood pressure
   • Electrolytes
   • Glucose
   • Weight monitoring
   • Symptoms of under-replacement (fatigue, weakness, nausea, hypotension)
   • Symptoms of over-replacement (weight gain, insomnia, edema) 1

2. Endocrinology consultation:

   • Early referral is appropriate for all patients with suspected or confirmed adrenal insufficiency 1

Special Considerations

• Tapering from exogenous steroids (if applicable):

  • Reduce dose by 10-20% every 1-2 weeks
  • Once at physiologic replacement dose, switch to alternate-day therapy
  • Final phase: reduce by 1 mg every 2-4 weeks until complete withdrawal or lowest effective dose 1

• Pregnancy considerations:

  • Hydrocortisone requirements may increase in third trimester
  • Plan for parenteral hydrocortisone during delivery 1

Pitfalls to Avoid

• Misinterpreting test results: The ACTH stimulation test should be interpreted in the clinical context, not just based on numerical cutoffs 2
• Inadequate stress dosing: Failure to adjust glucocorticoid doses during illness can lead to adrenal crisis
• Overlooking comorbidities: Patients with asthma and diabetes have higher risk of adrenal crisis 1
• Abrupt steroid discontinuation: Always taper steroids gradually to allow HPA axis recovery 1

The management of partial adrenal insufficiency requires careful monitoring and adjustment of replacement therapy based on clinical response. Early endocrinology consultation is essential for optimizing treatment and preventing complications.