Workup for Excessive Salt Craving and Night Sweats
Primary adrenal insufficiency must be excluded first as it is life-threatening and classically presents with both salt craving and constitutional symptoms including fatigue, weight loss, hyperpigmentation, nausea, and orthostatic hypotension. 1
Initial Diagnostic Approach
First-Line Laboratory Testing
Obtain the following tests simultaneously to establish the diagnosis:
- Morning cortisol and ACTH levels (measured simultaneously before 8 AM) - this is the first-line test for adrenal insufficiency 1
- Serum electrolytes: sodium, potassium, chloride, bicarbonate, creatinine, and glucose 2
- Spot or 24-hour urine collection: urine sodium, chloride, and osmolality 2
- Thyroid-stimulating hormone (TSH) - hyperthyroidism is one of the most frequent hormonal causes of excessive sweating 3
- Complete blood count and C-reactive protein - to evaluate for infectious or inflammatory causes of night sweats 4
Interpretation of Initial Results
For adrenal insufficiency:
- Basal cortisol <250 nmol/L with elevated ACTH is diagnostic of primary adrenal insufficiency 1
- Basal cortisol <400 nmol/L with elevated ACTH raises strong suspicion and warrants empiric treatment if clinically unstable 1
- If initial results are indeterminate, proceed with cosyntropin stimulation testing 1
For renal salt wasting syndromes (if hypokalemia with metabolic alkalosis is present):
- Bartter syndrome: elevated urinary chloride (>20 mEq/L), elevated plasma renin activity, normal to low blood pressure 1, 2
- Gitelman syndrome: hypomagnesemia and hypocalciuria (urinary calcium-to-creatinine ratio <0.2) distinguish this from Bartter syndrome 1, 2
Secondary Testing Based on Initial Results
If Adrenal Insufficiency is Suspected
- Plasma aldosterone and renin activity with calculation of aldosterone-to-renin ratio 2
- Consider imaging of adrenal glands if primary adrenal insufficiency is confirmed 5
If Renal Salt Wasting is Suspected
- Genetic testing for Bartter syndrome genes (SLC12A1, KCNJ1, CLCNKB, BSND, CASR) 1, 2
- Genetic testing for Gitelman syndrome (SLC12A3 mutations) 1, 2
If Night Sweats Predominate Without Clear Cause
- Tuberculosis testing 4
- HIV testing 4
- Chest radiography 4
- Consider CT chest/abdomen if lymphoma or malignancy is suspected 4
- Evaluate for menopause (in women), mood disorders, GERD, and obesity as these are commonly associated with night sweats 4
Critical Pitfalls to Avoid
Do not confuse cerebral salt wasting with SIADH - these require opposite treatments (volume replacement vs. fluid restriction), and cerebral salt wasting presents with hyponatremia, volume depletion, and inappropriately high renal sodium loss (>20 mmol/L), typically in the context of intracranial pathology 1, 2
Do not overlook medication history - patients on chronic corticosteroids (≥20 mg/day prednisone equivalent for ≥3 weeks) who develop salt craving and hypotension should be presumed to have iatrogenic secondary adrenal insufficiency 1
Do not dismiss psychiatric history - women with documented cognitive or psychiatric disorders, particularly depression, are susceptible to psychogenic salt poisoning 6
Do not assume night sweats alone indicate serious pathology - most patients with persistent night sweats in primary care do not have a serious underlying disorder, but systematic evaluation is still warranted 4
Treatment Considerations
If primary adrenal insufficiency is confirmed:
- Hydrocortisone 15-25 mg daily in divided doses 1
- Fludrocortisone 50-200 µg daily 1
- Patients should eat sodium salt and salty foods without restriction to avoid salt craving 5
If Bartter syndrome is confirmed:
- Pharmacologic doses of sodium chloride supplementation (5-10 mmol/kg/day) combined with potassium chloride 2
- Consider NSAIDs (indomethacin or ibuprofen) in symptomatic patients, especially in early childhood 2
If Gitelman syndrome is confirmed: