Darkening of the Palm Creases and Tongue: A Case of Hyponatremia Due to Primary Adrenal Insufficiency

Hyponatremia is a common electrolyte disorder among hospitalized patients. The differential diagnosis is complex, and detailed history, physical examination and step-wise approach for the evaluation of hyponatremia is needed.

Case Description:

A 49-year-old Caucasian female with a history of Hashimoto thyroiditis presented to the emergency department for evaluation of dizziness, nausea and vomiting. The patient was found to be hypotensive, with a blood pressure of 82/56 mm Hg. Darkening of the palm creases and tongue was noted. Laboratory data revealed serum sodium 110 mEq/L, potassium 5.1 meq/L, serum osmolality 239 mosm/kg, urinary sodium 94 meq/L, and urinary osmolarity 381 mosm/kg. Thyrotropin levels were normal. The 250 microgram adrenocorticotropic hormone (ACTH) stimulation test confirmed the diagnosis of adrenal insufficiency.

Discussion:

Primary adrenal insufficiency is a potentially life-threatening condition, defined by the inability of the adrenal glands to produce sufficient amounts of glucocorticoids and mineralocorticoids, which results in results in urinary sodium loss and hyponatremia. Orthostatic hypotension, hyperkalemia, and hypoglycemia are frequently noted. Hyperpigmentation of the skin, tongue and mucous membranes is caused by excessive adrenocorticotropin hormone binding to the melanocortin 1 receptor on melanocytes to produce melanin.

In summary, the darkening of the palm creases and tongue in the setting of hyponatremia merits high suspicion and appropriate diagnostic workup for primary adrenal insufficiency.