Thanks to Jess for presenting the fascinating case of a middle-aged woman with family history of autoimmune disease who presented with acute onset of fatigue and abdominal pain, found to have vitiligo on exam. Work up revealed hyponatremia due to a secondary adrenal insufficiency, pancytopenia, and panhypopituitarism possibly due to a yet to be diagnosed autoimmune disorder!
- Remember that hyponatremia is a problem of water regulation that can be compounded by low solute intake.
- Primary adrenal insufficiency is disorder at the level of the adrenal glands and manifests with low sodium and high serum potassium levels.
- Secondary adrenal insufficiency is disorder at the level of the pituitary and manifests with low/normal sodium and normal potassium levels (because low cortisol leads to high ADH levels and hyponatremia).
- Make sure to do work up to rule out panhypopituitarism. Keep in mind that the most sensitive test for HPA access integrity is LH/FSH.
- Tertiary adrenal insufficiency is disorder at the level of the hypothalamus and presents similarly to secondary AI.
- Test for adrenal insufficiency with a cort-stim test and/or AM cortisol and ACTH levels.
Remember these three steps to working up hyponatremia:
- Is there a sodium problem? check serum osm
- Are the kidneys responding appropriately? check urine osm
- Is ADH revved up for a hemodynamic reason? check urine Na
- Failure of adrenal glands
- Causes: Addison’s (most common in the US), infiltrative processes (TB, sarcoid), hemorrhage, toxins
- Labs would show ↓Na and ↑potassium (b/c aldosterone is gone)
- Failure of pituitary (low ACTH)
- Causes: pituitary lesions, surgeries, TBI, drugs
- Clinically may present with loss of other anterior pituitary hormones
- Labs would show ↓Na (because low cortisol leads to high ADH levels) but normal potassium levels (b/c aldosterone is active)
- Failure of hypothalamus (low CRH)
- Causes: more commonly iatrogenic (cessation of high dose glucocorticoid therapy without taper) or post surgical interventions.
- Inflammation of the pituitary
- Four categories based on histologic findings:
- Most common form
- Seen in late pregnancy and post-partum period
- Also associated with CTLA4 inhibitors like ipilimumab
- Idiopathic or secondary to GPA, sarcoid, TB
- Plasmacytic (IgG4-related)
- Xanthomatous (most rare)
- Clinical presentation
- Headache out of proportion to exam findings
- Preferential decrease in ACTH and TSH ⇒ adrenal insufficiency and hypothyroidism
- Pituitary size eventually normalizes but pituitary loss of function is often permanent.