Laboratory Monitoring of Addison's Disease
Patients with Addison's disease require annual monitoring with serum sodium and potassium, thyroid function tests, plasma glucose and HbA1c, complete blood count, and vitamin B12 levels, with clinical assessment of weight and blood pressure at each visit. 1, 2
Core Annual Laboratory Tests
The following laboratory tests should be performed annually in all patients with established Addison's disease:
- Serum sodium and potassium to detect hyponatremia or hyperkalemia, which indicate inadequate glucocorticoid replacement or excessive fludrocortisone dosing 1, 2
- Thyroid function tests (TSH, free T4, and thyroid peroxidase antibodies) every 12 months to screen for autoimmune hypothyroidism, which commonly coexists with autoimmune Addison's disease 1, 2
- Plasma glucose and HbA1c annually to detect diabetes mellitus, an associated autoimmune condition 1, 2
- Complete blood count annually to screen for anemia, which may indicate pernicious anemia from autoimmune gastritis 1, 2
- Vitamin B12 levels annually, as B12 deficiency due to autoimmune gastritis is common in these patients 1, 2
Clinical Monitoring Parameters at Each Visit
Beyond laboratory tests, clinical assessment is essential:
- Weight measurement at each visit to detect under-replacement (weight loss) or over-replacement (weight gain) 1, 2
- Blood pressure assessment, including postural measurements, to detect postural hypotension (indicating insufficient mineralocorticoid therapy) or hypertension (indicating fludrocortisone excess) 1, 2
- Assessment of general health and well-being, with specific questioning about energy levels, morning nausea, appetite, and timing of symptom patterns to guide dose adjustments 2
Mineralocorticoid-Specific Monitoring
- Plasma renin activity can be valuable in patients with features of mineralocorticoid deficiency, though it is not routinely required in all patients on fludrocortisone replacement 1, 3
- Fludrocortisone dosing should be guided by blood pressure, serum electrolytes, and assessment of salt cravings 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, 2
Critical Monitoring Pitfalls to Avoid
Serum cortisol levels are not useful for monitoring adequacy of replacement therapy, as hydrocortisone produces highly variable peaks and troughs throughout the day, making interpretation impossible 2, 3. Similarly, ACTH levels do not guide dose adjustments in established Addison's disease, as they remain elevated regardless of replacement adequacy 2. While one older study suggested diurnal cortisol profiles could be useful 3, current consensus guidelines emphasize that clinical parameters (weight, blood pressure, electrolytes, and patient symptoms) are far more reliable for monitoring than hormonal measurements 1, 2.
Do not overlook screening for associated autoimmune conditions, as continuous surveillance is necessary given the high prevalence of polyglandular autoimmune syndromes 2. The American College of Endocrinology emphasizes that patients with autoimmune Addison's disease require lifelong follow-up and surveillance for these conditions 1, 4.
Special Considerations
- During pregnancy, monitoring should be based on blood pressure, serum electrolytes, and assessment of salt cravings rather than plasma renin activity 2
- In patients who develop hypertension, reduce fludrocortisone dose if there are signs of mineralocorticoid excess; if renin is elevated or upper-normal without signs of excess, use ACE inhibitors or angiotensin II receptor antagonists without changing fludrocortisone 5
- Continuous glucose monitoring may be considered in select patients with suspected nocturnal hypoglycemia, particularly those on regimens resulting in low early-morning cortisol levels 6