Laboratory Evaluation of Endocrine Causes of ICU Hypoglycemia

Adrenal Evaluation

Measure baseline morning cortisol and ACTH levels before initiating any corticosteroid therapy in ICU patients with unexplained hypoglycemia. 2
Perform a corticotropin (ACTH) stimulation test as the confirmatory diagnostic test for adrenal insufficiency when the patient’s condition allows. 2
Obtain serum sodium and potassium to detect hyponatremia and hyperkalemia, which are diagnostic clues for adrenal insufficiency. 2
Recognize hyperpigmentation of skin or mucous membranes as a specific sign suggestive of primary adrenal insufficiency. 2
Consider unexplained fever or abdominal pain as possible manifestations of adrenal insufficiency in critically ill patients. 2

Order thyroid‑stimulating hormone (TSH) and free thyroxine (free T4) to assess thyroid function in ICU patients with hypoglycemia, noting that near‑normal TSH can coexist with markedly suppressed free T4, indicating true hypothyroidism rather than euthyroid sick syndrome. [1][2]

During a hypoglycemic episode, obtain plasma glucose, insulin, C‑peptide, and proinsulin levels to differentiate endogenous hyperinsulinism from other mechanisms. 1
Measure β‑hydroxybutyrate concentration to help identify non‑insulin‑mediated causes of hypoglycemia. 1
Screen the blood for oral hypoglycemic agents to rule out medication‑induced hypoglycemia. 1
Assess insulin antibodies to detect autoimmune hypoglycemia. 1

If adrenal crisis is clinically suspected, administer intravenous hydrocortisone 100 mg immediately without awaiting laboratory confirmation. 2
Delaying treatment of a suspected adrenal crisis is associated with increased mortality; therefore, do not wait for ACTH stimulation test results before initiating therapy. 2