What laboratory tests need to be monitored in a patient with Addison's disease?

Laboratory Monitoring in Addison's Disease

Patients with Addison's disease require annual monitoring of serum sodium and potassium, blood pressure, weight, thyroid function tests, plasma glucose and HbA1c, complete blood count, and vitamin B12 levels to detect complications of replacement therapy and screen for associated autoimmune conditions. 1

Core Annual Laboratory Tests

The following labs should be checked at least annually in all patients with Addison's disease:

• Serum electrolytes (sodium and potassium) must be measured annually to detect hyponatremia or hyperkalemia, which indicate inadequate glucocorticoid replacement or excessive fludrocortisone dosing 1
• Thyroid function tests (TSH, free T4, and thyroid peroxidase antibodies) should be performed every 12 months, as autoimmune hypothyroidism commonly coexists with autoimmune Addison's disease 1
• Plasma glucose and HbA1c require annual screening to detect diabetes mellitus, another associated autoimmune condition 1
• Complete blood count should be checked annually to screen for anemia, which may indicate pernicious anemia from autoimmune gastritis 1
• Vitamin B12 levels need annual assessment, as B12 deficiency due to autoimmune gastritis is common in these patients 1

Clinical Monitoring Parameters

Beyond laboratory tests, several clinical parameters guide therapy adjustments:

• Weight measurement at each visit detects under-replacement (weight loss) or over-replacement (weight gain) 1
• Blood pressure assessment, including postural measurements, is essential—postural hypotension indicates insufficient mineralocorticoid therapy or low salt intake, while hypertension suggests fludrocortisone excess 1
• Assessment of symptoms including energy levels, morning nausea, appetite, salt cravings, and timing of symptom patterns helps guide dose adjustments 1

Mineralocorticoid-Specific Monitoring

For patients on fludrocortisone replacement:

• Plasma renin activity can be valuable in patients with features of mineralocorticoid deficiency, though it is not routinely required 1
• Blood pressure and serum electrolytes together guide fludrocortisone dosing, with typical doses ranging from 50-200 µg daily 1, 2

Bone Health Surveillance

• Bone mineral density should be assessed every 3-5 years to monitor for glucocorticoid-induced osteoporosis, a complication of chronic replacement therapy 1, 3

Important Monitoring Pitfalls to Avoid

• Do not use serum cortisol levels to monitor adequacy of replacement therapy—hydrocortisone produces highly variable peaks and troughs throughout the day, making interpretation impossible 1, 4
• ACTH levels do not guide dose adjustments in established Addison's disease, as they remain elevated regardless of replacement adequacy 1
• Do not overlook screening for associated autoimmune conditions—continuous surveillance is necessary as new autoimmune diseases can develop over time 1

Special Monitoring Considerations

• During pregnancy, monitoring should be based on blood pressure, serum electrolytes, and assessment of salt cravings, with small dose adjustments to both hydrocortisone and fludrocortisone potentially needed in the third trimester 1
• Patients on long-term systemic steroids for other conditions may require additional monitoring including hypothalamic-pituitary-adrenal axis suppression testing and ophthalmologic examination 5
• Continuous glucose monitoring may be considered in select patients with symptoms suggesting nocturnal hypoglycemia, particularly those with early morning symptoms despite standard replacement regimens 6