To which specialist should a patient with primary hyperparathyroidism (PHPT), hypercalcemia, and elevated parathyroid hormone (PTH) levels be referred?

Specialist Referral for Primary Hyperparathyroidism

Patients with confirmed primary hyperparathyroidism (PHPT) should be referred to both an endocrinologist for medical management and a high-volume parathyroid surgeon for surgical evaluation. 1, 2, 3

Initial Referral to Endocrinology

The endocrinologist plays a critical role in confirming the diagnosis, excluding secondary causes, and determining surgical candidacy. 1, 2

Key responsibilities of the endocrinologist include:

• Confirming PHPT by measuring serum calcium (corrected for albumin) and intact PTH simultaneously, ensuring PTH is elevated or inappropriately normal in the setting of hypercalcemia 1, 2, 3
• Excluding vitamin D deficiency (target 25-OH vitamin D >20 ng/mL or 50 nmol/L) before finalizing the diagnosis, as deficiency causes secondary hyperparathyroidism that mimics PHPT biochemically 4, 2, 3
• Assessing dietary calcium intake through detailed history, as calcium deprivation can produce similar biochemical findings 4
• Evaluating for surgical indications including: corrected calcium >1 mg/dL (0.25 mmol/L) above upper limit of normal, age <50 years, impaired kidney function (GFR <60 mL/min/1.73 m²), osteoporosis (T-score ≤-2.5), history of nephrolithiasis or nephrocalcinosis, or hypercalciuria (>300 mg/24hr) 1, 2, 3

Important caveat: PTH assays vary significantly between laboratories—measurements can differ by up to 47% between different assay generations—so always use assay-specific reference values when interpreting results. 1, 3 PTH is more stable in EDTA plasma than serum and should be measured at least 12 hours after any previous dose if the patient is on treatment. 1, 3

Referral to High-Volume Parathyroid Surgeon

All patients meeting surgical criteria should be referred to an experienced, high-volume parathyroid surgeon (not just any general surgeon), as outcomes are significantly better with specialized expertise. 1, 5

The surgical referral is appropriate when:

• Any of the surgical indications listed above are met 1, 2, 3
• The patient has symptomatic disease (renal symptoms, bone disease, gastrointestinal complaints, psychiatric symptoms, or fatigue), even if biochemical values are only mildly elevated 6, 5, 7
• Hypercalcemia persists despite medical optimization 3

Critical pitfall to avoid: Do not delay surgical referral for years while attempting medical management in patients who meet surgical criteria. Studies show 24% of patients experience delays exceeding 2 years between diagnosis and surgery, during which time they develop severe complications including renal disease, osteoporosis, and psychiatric symptoms. 6 Even patients with "asymptomatic" PHPT often have vague nonspecific complaints that improve dramatically after parathyroidectomy. 5

Special Consideration: Normal or Low-Normal PTH

Patients with hypercalcemia and PTH in the normal range (even as low as 40 pg/mL) can still have PHPT—the PTH is "inappropriately normal" for the degree of hypercalcemia. 1, 7, 8 These patients are typically younger, more symptomatic, and have higher rates of multiglandular disease (59% vs 32%). 8 They should still be referred to endocrinology and surgery, as cure rates are similar (97%) to those with elevated PTH. 7, 8

Medical Management for Non-Surgical Candidates

If parathyroidectomy is contraindicated or the patient refuses surgery, the endocrinologist manages with:

• Cinacalcet (calcimimetic) starting at 30 mg twice daily, titrated to normalize serum calcium 9
• Maintaining normal calcium intake (1000-1200 mg/day, not exceeding 2000 mg/day total) 3
• Ensuring adequate vitamin D (>20 ng/mL) with supplementation if needed 2, 3
• Monitoring serum calcium monthly initially, then every 2 months once stable 9

Important limitation: Cinacalcet is FDA-approved for hypercalcemia in primary HPT only when parathyroidectomy would be indicated based on serum calcium levels but the patient is unable to undergo surgery. 9 It is not a substitute for appropriate surgical referral in surgical candidates.

Coordination Between Specialists

The endocrinologist and surgeon should work collaboratively, with the endocrinologist optimizing vitamin D status and calcium levels preoperatively, and the surgeon performing preoperative localization imaging (ultrasound and/or 99mTc-sestamibi SPECT/CT) only after biochemical diagnosis is confirmed. 2, 3 Never order parathyroid imaging before confirming the biochemical diagnosis—imaging is for surgical planning, not diagnosis. 3

For patients with suspected hereditary syndromes (MEN 2A, MEN 2B, or hyperparathyroid-jaw tumor syndrome), genetic counseling and germline testing should be considered, with management coordinated between endocrinology, surgery, and genetics. 1