What is the treatment approach for a patient with Addison's disease and hypothyroidism, including medication doses and duration?

Treatment of Addison's Disease with Concurrent Hypothyroidism

In patients with both Addison's disease and hypothyroidism, you must always initiate glucocorticoid replacement before starting thyroid hormone replacement to prevent precipitating a potentially fatal adrenal crisis. 1

Critical Treatment Sequence

Start hydrocortisone first, stabilize the patient, then add levothyroxine. This is non-negotiable because thyroid hormone increases cortisol metabolism and clearance, which can unmask or worsen adrenal insufficiency in an untreated patient with Addison's disease 1, 2.

Glucocorticoid Replacement (Start First)

Initial Dosing

• Hydrocortisone 15-25 mg daily divided into 2-3 doses is the standard starting regimen 1, 3
• Administer two-thirds of the daily dose immediately upon awakening and one-third in early afternoon (at least 6 hours before bedtime) to mimic physiological cortisol rhythm 1, 3
• A typical schedule is 10 mg upon awakening and 5 mg in early afternoon for a 15 mg total daily dose 3

Dose Titration

• Use the lowest effective dose that maintains well-being while minimizing side effects 1
• Titrate based on clinical symptoms including energy patterns, mental concentration, daytime somnolence, and signs of over-replacement (bruising, thin skin, edema, weight gain, hypertension, hyperglycemia) 4, 3
• Do not use plasma ACTH or serum cortisol levels to guide dose adjustments—these are not useful for monitoring 3, 2

Mineralocorticoid Replacement (Start Concurrently with Hydrocortisone)

• Fludrocortisone 0.05-0.1 mg once daily is the starting dose 1, 3
• Adjust based on volume status, sodium levels, blood pressure, and renin response (target upper half of reference range) 4, 3
• Final dose typically ranges from 50-200 μg daily 1, 2
• Patients should consume salt and salty foods freely and avoid licorice and grapefruit juice 1

Thyroid Hormone Replacement (Start After Glucocorticoid Stabilization)

• Only initiate levothyroxine after the patient is stabilized on hydrocortisone and fludrocortisone replacement 1
• Standard levothyroxine dosing for hypothyroidism applies once adrenal replacement is adequate
• Monitor thyroid function periodically, as autoimmune hypothyroidism commonly coexists with autoimmune Addison's disease 1, 2

Duration of Treatment

Both conditions require lifelong hormone replacement therapy—this is permanent treatment, not temporary. 1

Stress Dosing Protocols

Minor Illness or Stress

• Double or triple the oral hydrocortisone dose during febrile illness or minor procedures 1, 3
• Continue doubled dose for 24-48 hours after stress resolves 3

Major Surgery

• Administer 100 mg hydrocortisone IM before anesthesia 1, 3
• Follow with 100 mg IM every 6 hours postoperatively until patient can eat and drink 3
• Then double oral dose for 48+ hours before gradually reducing to maintenance 3

Adrenal Crisis (Life-Threatening Emergency)

• Immediate treatment with 100 mg IV or IM hydrocortisone, then 100 mg every 6-8 hours until recovery 1
• Administer isotonic (0.9%) saline at 1 L/hour initially until hemodynamic improvement (typically 3-4 L over 24-48 hours) 1
• Identify and treat the underlying precipitant 1

Essential Patient Education

• Provide emergency injectable hydrocortisone kit and training on its use 1, 3
• Issue medical alert bracelet/necklace and steroid emergency card 1, 3, 2
• Educate on stress dosing for sick days and when to seek immediate medical attention 1, 3
• Teach recognition of under-replacement (fatigue, nausea, salt craving) and over-replacement (weight gain, hypertension, hyperglycemia) signs 2

Monitoring Schedule

• Annual visits minimum with assessment of general health, weight, blood pressure, and serum electrolytes 1, 2
• Check thyroid function periodically given high prevalence of concurrent autoimmune thyroid disease 2
• Assess bone mineral density every 3-5 years to monitor for glucocorticoid-induced osteoporosis 1, 2
• Screen for other autoimmune conditions including diabetes mellitus, pernicious anemia, and celiac disease 2

Common Pitfall to Avoid

The most dangerous error is starting thyroid hormone replacement before or without adequate glucocorticoid replacement, which can precipitate acute adrenal crisis by increasing cortisol metabolism 1. Always establish stable hydrocortisone and fludrocortisone replacement first, then add levothyroxine.