What are the implications and treatment options for a patient with hyperparathyroidism indicated by a high Parathyroid Hormone (PTH) level?

Management of Elevated PTH at 9.8 pmol/L

Your patient requires immediate evaluation of serum calcium, phosphorus, 25-OH vitamin D, and kidney function to determine whether this represents primary, secondary, or tertiary hyperparathyroidism, as the treatment pathway differs fundamentally based on the underlying cause. 1, 2

Initial Diagnostic Workup

Check the following labs immediately:

• Serum calcium (total and ionized) to distinguish primary from secondary hyperparathyroidism 1, 2
• Serum phosphorus to assess for CKD-related mineral bone disorder 3, 1
• 25-OH vitamin D level (target ≥30 ng/mL) 1, 2
• Kidney function (eGFR/creatinine) as PTH rises early in CKD before calcium/phosphorus changes 1, 2
• Bone alkaline phosphatase if bone disease is suspected 3

Review all medications that affect calcium metabolism, particularly calcium supplements, vitamin D, thiazide diuretics, and lithium 1, 2

Treatment Algorithm Based on Underlying Etiology

If Hypercalcemia is Present (Primary or Tertiary Hyperparathyroidism)

With calcium >2.37 mmol/L (9.5 mg/dL):

• Parathyroidectomy is indicated if PTH >800 pg/mL (88 pmol/L) with hypercalcemia and/or hyperphosphatemia refractory to medical therapy 1, 2
• For PTH levels between 100-500 pg/mL (11-55 pmol/L) with unexplained hypercalcemia, bone pain, or elevated bone alkaline phosphatase, consider bone biopsy before surgery to confirm hyperparathyroid bone disease 3, 1
• Surgical options include subtotal parathyroidectomy or total parathyroidectomy with autotransplantation 1, 2
• Cinacalcet 30 mg twice daily can be initiated and titrated every 2-4 weeks (30 mg BID → 60 mg BID → 90 mg BID → 90 mg TID-QID) to normalize calcium in patients unable to undergo surgery 4

If Normocalcemia or Hypocalcemia is Present (Secondary Hyperparathyroidism)

For CKD Stage 3a-5 not on dialysis:

• Correct vitamin D deficiency first: supplement with cholecalciferol or ergocalciferol to achieve 25-OH vitamin D ≥30 ng/mL 1, 2
• Address modifiable factors: hyperphosphatemia, high phosphate intake, and hypocalcemia 3
• Do not routinely use calcitriol or vitamin D analogs in non-dialysis CKD patients; reserve for severe and progressive hyperparathyroidism in CKD G4-G5 3
• Implement dietary phosphate restriction if hyperphosphatemia is present 1, 2

For CKD Stage 5 on dialysis:

• Target PTH range is 2-9 times the upper normal limit (approximately 150-300 pg/mL or 16.5-33 pmol/L) 3
• Initiate cinacalcet 30 mg once daily if PTH >300 pg/mL (33 pmol/L), titrating every 2-4 weeks through sequential doses of 30,60,90,120, and 180 mg once daily 4
• Alternatively, use calcitriol or vitamin D analogs (paricalcitol, doxercalciferol), or combination therapy with calcimimetics 3
• Intravenous calcitriol is more effective than oral for lowering PTH in dialysis patients 3
• Use dialysate calcium concentration between 1.25-1.50 mmol/L (2.5-3.0 mEq/L) 3

Critical Monitoring Parameters

During initial treatment phase:

• Serum calcium and phosphorus: weekly for first month, then monthly for 3 months, then every 3 months 3, 1, 2
• PTH levels: every 1-4 weeks after initiation/dose adjustment, then every 3 months once stable 3, 1, 2

If calcium falls below 2.1 mmol/L (8.4 mg/dL) but remains above 1.88 mmol/L (7.5 mg/dL):

• Increase calcium-containing phosphate binders and/or vitamin D sterols 4

If calcium falls below 1.88 mmol/L (7.5 mg/dL) or symptomatic hypocalcemia develops:

• Withhold cinacalcet or vitamin D therapy until calcium reaches 2.0 mmol/L (8 mg/dL) and symptoms resolve 3, 4
• Reinitiate at next lowest dose 4

Important Clinical Pitfalls

PTH levels between 100-500 pg/mL (11-55 pmol/L) in CKD have insufficient sensitivity and specificity to predict bone disease type (adynamic bone vs. hyperparathyroid bone disease) 3

Avoid oversuppression of PTH in dialysis patients: PTH <65 pg/mL (7.15 pmol/L) is associated with nearly universal adynamic bone disease, which increases risk of hypercalcemia and vascular calcification 3

Do not use cinacalcet in CKD patients not on dialysis due to increased hypocalcemia risk 4

For patients with aluminum exposure history, obtain bone biopsy before parathyroidectomy to exclude coexistent aluminum bone disease, as parathyroid ablation can worsen aluminum toxicity 3