Is salt craving more suggestive of primary or secondary adrenal insufficiency?

Salt Craving in Adrenal Insufficiency: Primary vs Secondary

Salt craving is more suggestive of primary adrenal insufficiency rather than secondary adrenal insufficiency, as it indicates mineralocorticoid deficiency which is characteristic of primary adrenal insufficiency. 1

Pathophysiological Basis

• In primary adrenal insufficiency (PAI), there is destruction or dysfunction of the adrenal cortex, leading to deficiency of all adrenocortical hormones including mineralocorticoids (aldosterone) 2
• Secondary adrenal insufficiency results from pituitary dysfunction affecting ACTH production, which primarily impacts cortisol production while preserving aldosterone secretion (as aldosterone is mainly regulated by the renin-angiotensin system) 2
• Salt craving occurs due to mineralocorticoid deficiency, which causes sodium loss and disruption of electrolyte balance 1, 3

Clinical Differentiation

Primary Adrenal Insufficiency Features:

• Salt craving is a characteristic symptom due to aldosterone deficiency 1
• Patients are advised to eat sodium salt and salty foods without restriction as part of treatment 1
• Other associated findings include:
  • Hyperpigmentation (due to elevated ACTH) 4
  • Hyperkalemia 5
  • Hyponatremia 5
  • Postural hypotension 1

Secondary Adrenal Insufficiency Features:

• Typically lacks salt craving as mineralocorticoid production remains largely intact 2
• No hyperpigmentation (ACTH is low) 2
• Less severe or absent electrolyte disturbances 2
• May still have fatigue, weakness, and glucocorticoid deficiency symptoms 6

Diagnostic Implications

• The presence of salt craving should prompt evaluation for primary adrenal insufficiency 1, 5
• Mineralocorticoid replacement is evaluated clinically by asking patients about salt cravings, measuring blood pressure in supine and standing positions, and identifying peripheral edema 1
• Under-replacement of mineralocorticoids is common and sometimes compensated for by over-replacement of glucocorticoids 1, 3

Treatment Considerations

• Patients with primary adrenal insufficiency require both glucocorticoid and mineralocorticoid replacement 7, 8
• Most patients with primary adrenal insufficiency should take 50–200 μg fludrocortisone as a single daily dose 9
• Allowing unrestricted sodium intake and avoiding salt craving is an important component of substitution therapy 1
• Mineralocorticoid replacement is not typically required in secondary adrenal insufficiency 2

Clinical Pearls

• Salt craving can be used as a clinical indicator to monitor adequacy of mineralocorticoid replacement in primary adrenal insufficiency 9
• Persistent salt craving despite adequate sodium intake may indicate the need for increased fludrocortisone dose 9
• Patients should avoid potassium-containing salts which are often marketed as "healthy" 1
• Avoid liquorice and grapefruit juice as they potentiate the mineralocorticoid effect of hydrocortisone 9

Remember that salt craving is a valuable diagnostic clue that helps distinguish primary from secondary adrenal insufficiency and guides appropriate replacement therapy.