Urgent Evaluation and Management of ACTH‑Independent Cushing Syndrome with Concurrent Hyperinsulinemic Hypoglycemia

Diagnostic Criteria

Suppressed ACTH with markedly elevated serum cortisol identifies an adrenal source of Cushing syndrome (NCCN guidelines) 1, 2.
Adrenal masses larger than 5 cm or showing inhomogeneous, irregular margins are radiologic hallmarks of malignancy and mandate staging imaging of the chest, abdomen, and pelvis (NCCN guidelines) 1.
A non‑contrast Hounsfield unit (HU) measurement > 10 on CT suggests either malignancy or pheochromocytoma and should trigger plasma metanephrine testing before any surgical intervention (The Journal of Urology) 3.
24‑hour urinary free cortisol > 193 nmol/24 h confirms hypercortisolism (Nature Reviews Endocrinology) 4.

Contrast‑enhanced abdominal CT is the first‑line modality to characterize adrenal lesions; it provides size, margin, and HU data (NCCN; The Journal of Urology) 1, 3.
If CT is equivocal, chemical‑shift MRI should be performed to detect microscopic fat, which is diagnostic of a lipid‑rich adenoma (The Journal of Urology) 3.

Fasting glucose < 3 mmol/L with inappropriately high insulin levels (> 75 µU/mL) strongly supports insulinoma (guideline consensus) 5.

Patients should be instructed to carry rapid‑acting carbohydrate (e.g., glucose tablets) and consume 4–8 oz of juice at the first sign of symptoms (American Family Physician) 6.
A medical‑alert bracelet indicating hypoglycemia risk is recommended (American Family Physician) 6.

Ketoconazole 400–1200 mg/day is the most frequently used agent for rapid cortisol reduction (NCCN; Annals of Oncology) 1, 7.
Metyrapone is an effective alternative and can be combined with other steroidogenesis inhibitors (NCCN; Annals of Oncology) 1, 7.

Benign cortisol‑producing adenomas are best treated with laparoscopic adrenalectomy (NCCN) 1, 2.
Open adrenalectomy is advised for tumors > 5 cm, those with malignant imaging features, or confirmed carcinoma (NCCN) 1.
Post‑operative physiologic hydrocortisone replacement (15–20 mg daily in divided doses) is required until recovery of the hypothalamic‑pituitary‑adrenal axis (Journal of Clinical Oncology) 8, 9.
For confirmed adrenal carcinoma, adjuvant mitotane therapy is recommended (Annals of Oncology) 7.

All patients undergoing adrenalectomy must receive stress‑dose steroids (hydrocortisone 50–100 mg IV every 6–8 h) perioperatively to prevent adrenal crisis (Journal of Clinical Oncology) 8, 9, 10.

Immediate endocrinology consultation is essential for coordinating diagnostic imaging, medical therapy of hypercortisolism, peri‑operative steroid planning, and long‑term hormone replacement education (Journal of Clinical Oncology) 8, 9, 11.
Management should involve a multidisciplinary team including endocrinology, endocrine surgery, and interventional radiology (NCCN) 1, 2.

Screen for catecholamine excess (plasma metanephrines) before any adrenal surgery when HU > 10; failure to do so can precipitate a fatal hypertensive crisis under anesthesia (The Journal of Urology) 3.

All statements are derived from cited guideline sources; evidence levels were not explicitly specified in the source material.

Collect at least two 24‑hour urinary free cortisol (UFC) samples to confirm hypercortisolism and to accommodate intra‑patient variability that can reach ≈ 50 % 12.

Assess creatinine clearance before interpreting UFC results; values < 60 mL/min render UFC unreliable and warrant use of alternative tests such as late‑night salivary cortisol 12.

Verify urinary creatinine excretion to ensure complete 24‑hour urine collection, because incomplete collections invalidate UFC measurements 12.
Avoid reliance on a single UFC measurement; averaging multiple collections improves diagnostic accuracy 12.

Recognize that oral estrogen therapy, pregnancy, and chronic active hepatitis raise corticosteroid‑binding globulin (CBG) levels, which can artificially increase total serum cortisol and produce false‑positive results 12.