secondary adrenal insufficiency (SAI)

Introduction

Adrenal insufficiency due to pituitary insufficiency. Only glucocorticoid synthesis is affected. The renin-angiotensin- aldosterone axis remains intact.

Etiology

• suppression of the hypothalamic-pituitary-adrenal axis
  • exogenous glucocorticoids (most common) or ACTH
  • post surgical treatment for Cushing's disease
  • chronic administration of drugs with corticosteroid activity: megestrol (Megace)
• pituitary or hypothalamic lesion resulting in ACTH deficiency
  • tumors
    • pituitary adenoma
    • craniopharyngioma or Rathke cyst
    • hypothalmic tumor
    • sarcoidosis
    • metastatic tumor
  • surgery or trauma
  • cranial irradiation
  • pituitary infarction (Sheehan's syndrome)
  • infectious or autoimmune adenohypophysitis

Clinical manifestations

• signs & symptoms milder than Addison's disease
• no salt craving or postural dizziness
• tachycardia, nausea, weakness, dizziness, & hyponatremia
• pigmentation absent
• no dehydration, only slight decrease in blood pressure
• other obnormalities of hypothalamic or pituitary function may be present

Laboratory

• cosyntropin (Cortrosyn) stimulation test
  • generally increased response
  • in long-standing disease, repeated daily injections of ACTH may be necessary to prime adrenal gland
• serum Na+: hyponatremia is often present
• serum K+: hyperkalemia is NOT a feature
• serum ACTH: low or inappropriately normal
• serum cortisol (NOT generally useful)
  • useful in the setting of acute pituitary injury
  • in the setting of acute stress, a normal serum cortisol is 20-120 ug/dL
• serum aldosterone: normal
• plasma renin: normal
• insulin tolerance test
• metyrapone stimulation test

Radiology

• MRI of the pituitary & hypothalamus

Management

• glucocorticoid
  • prednisone 5 mg PO qAM & 2.5 mg PO qPM
  • hydrocortisone 12-15 mg/m2/day (20-25 mg QD)
  • for minor illness, stress, fever > 100 F, influenza
    • double the oral maintenance dose
  • for severe illness or injury
    • hydrocortisone 100-150 mg/day IV divided every 6 hours
    • septic shock: 150-200 mg/day
  • do not use dexamethasone for chronic glucocorticoid replacement therapy
• mineralocorticoid replacement generally not necessary
• patient education
• glucocorticoid coverage at times of stress is indicated in patients who have taken potentially suppressive doses of glucocorticoids for more than 3 weeks the preceding year

More general terms

• adrenal insufficiency

Additional terms

• ACTH deficiency (central adrenal insufficiency)
• Addison's disease (primary adrenal failure)