What additional preoperative tests should be performed before endocrine surgery?

Preoperative Testing Before Endocrine Surgery

All patients undergoing endocrine surgery require comprehensive biochemical screening to identify hormone hypersecretion and assess for functional tumors, with specific testing dictated by the type of endocrine pathology and surgical site. 1

Essential Testing by Endocrine Pathology

For Adrenal Masses/Incidentalomas

Mandatory biochemical evaluation includes:

• 1-mg overnight dexamethasone suppression test for all patients to screen for autonomous cortisol secretion (cortisol >5.0 mg/dL suggests subclinical Cushing syndrome) 1
• Plasma free metanephrines and normetanephrines to exclude pheochromocytoma—this must be done before ANY adrenal surgery to prevent intraoperative hypertensive crisis 1, 2
• Plasma aldosterone-to-renin ratio (ARR) if hypertensive (ARR >20 warrants further evaluation with 24-hour urine aldosterone after salt loading) 1

Critical pitfall: Failure to screen for pheochromocytoma before adrenal surgery can be fatal. Even if imaging suggests a benign adenoma, biochemical exclusion is mandatory 1, 2.

If hypercortisolism is confirmed, additional testing includes:

• Low or suppressed ACTH to confirm adrenal origin
• Assessment and optimization of diabetes and hypertension preoperatively
• Thromboembolic prophylaxis planning 1

For Thyroid Surgery (Medullary Carcinoma/MEN Syndromes)

Before any thyroid surgery when MTC is suspected:

• Basal serum calcitonin and CEA as tumor markers 3
• RET proto-oncogene mutation testing for all patients with MTC (even apparently sporadic cases—6% harbor germline mutations) 3
• Plasma free metanephrines/normetanephrines or 24-hour urinary fractionated metanephrines to screen for pheochromocytoma (MEN 2A/2B) 3, 4, 3
• Serum calcium and intact PTH to screen for hyperparathyroidism (MEN 2A) 3, 4
• Preoperative neck ultrasound (mandatory) 3
• Vocal cord mobility assessment 3

If pheochromocytoma is identified, it must be removed FIRST with α-adrenergic blockade (phenoxybenzamine) instituted at least 7-14 days preoperatively, followed by forced hydration before thyroid surgery 3, 2.

For Parathyroid Surgery

Preoperative evaluation includes:

• Serum calcium and intact PTH (contemporaneous measurement) 4
• 25-OH Vitamin D levels to exclude hypovitaminosis D as secondary cause and prevent postoperative hypocalcemia 4, 5
• Preoperative imaging: neck ultrasound with 99mTc-sestamibi scintigraphy with SPECT/CT 4, 5
• Intraoperative PTH assay (ioPTH) should be planned, particularly for minimally invasive approaches (Miami protocol: ≥50% reduction at 10 minutes post-resection predicts cure in 97%) 6, 7

For MEN1 patients: Open bilateral neck exploration is recommended (not minimally invasive) as all four glands are typically affected 5.

For Pituitary Surgery (Non-Functioning Adenomas)

Comprehensive anterior pituitary axis evaluation:

• Morning cortisol and ACTH (consider ACTH stimulation test if cortisol 3-15 mg/dL) 8
• TSH and free T4 8
• Prolactin (mandatory to exclude prolactinoma) 8
• IGF-1 to exclude clinically silent GH-secreting tumors 8
• LH, FSH, testosterone (males) or estrogen (premenopausal females) if symptoms suggest hypogonadism 8
• Electrolytes to assess for SIADH or diabetes insipidus 9

Replacement therapy for adrenal insufficiency and significant hypothyroidism must be initiated preoperatively 8.

General Perioperative Considerations

Patients on Chronic Glucocorticoids or with Adrenal Insufficiency

• Stress-dose corticosteroids are required perioperatively (hydrocortisone 50-100 mg IV Q6-8h initially, then taper to maintenance over 5-7 days) 9
• All patients need education on stress dosing, emergency injectables, and medical alert identification 9
• Endocrine consultation before surgery is appropriate for planning 9

Patients with Subclinical Cushing Syndrome

• Optimize diabetes and hypertension before surgery 1
• Implement thromboembolic prophylaxis (increased risk) 1
• Plan for postoperative adrenal insufficiency—these patients will require steroid coverage and careful withdrawal after unilateral adrenalectomy 1

Thyroid Dysfunction

• Overt hypothyroidism: Elective surgery should be postponed until euthyroid 10, 11
• Mild hypothyroidism: Can proceed safely 10
• Hyperthyroidism: Moderate-to-severe cases require achieving euthyroid state; mild cases can proceed with β-blockade 10, 11

What NOT to Do Routinely

Recent evidence shows that routine preoperative laboratory testing (CBC, CMP, coagulation studies) in healthy ASA class 1-2 patients undergoing elective thyroid/parathyroid surgery does not reduce complications and wastes over $2.6 million annually 12. These tests should be ordered only when indicated by:

• Specific comorbidities (hypertension, heart failure, chronic kidney disease, diabetes, liver disease)
• Medications (diuretics, ACE inhibitors, ARBs, NSAIDs, digoxin, anticoagulants)
• Findings on history and physical examination 13

Routine chest radiography and urinalysis are not indicated in asymptomatic patients 13.