How to manage abnormal intact Parathyroid Hormone (PTH) levels?

Management of Abnormal Intact Parathyroid Hormone (PTH) Levels

The management of abnormal intact PTH levels should be based on the underlying cause, with specific treatment protocols determined by whether PTH is elevated or suppressed, and tailored according to the patient's kidney function status. 1

Assessment of PTH Abnormalities

• Evaluate PTH levels in conjunction with serum calcium, phosphorus, and vitamin D status to determine the underlying cause of the abnormality 2
• Confirm primary hyperparathyroidism by measuring serum calcium and intact PTH simultaneously, with the hallmark finding being hypercalcemia or high-normal calcium with elevated or inappropriately normal PTH levels 2
• Use assay-specific reference ranges when interpreting PTH values, as different assay generations can affect clinical interpretation 2, 3
• Consider that PTH levels are influenced by multiple factors including race, age, BMI, and vitamin D status 2

Management of Secondary Hyperparathyroidism in CKD

For CKD Stages 3-4 (Not on Dialysis):

• If plasma intact PTH exceeds 70 pg/mL (Stage 3) or 110 pg/mL (Stage 4), restrict dietary phosphate intake first 1
• If dietary restriction is ineffective, initiate calcitriol or one of its analogs (alfacalcidol or doxercalciferol) 1
• Only start vitamin D therapy when serum calcium is <9.5 mg/dL and phosphorus is <4.6 mg/dL 1
• Monitor serum calcium and phosphorus monthly for the first 3 months after initiating therapy, then every 3 months; check PTH every 3 months 1

For CKD Stage 5 (On Dialysis):

• For patients with intact PTH >300 pg/mL, administer active vitamin D sterols (calcitriol, alfacalcidol, paricalcitol, or doxercalciferol) to reduce PTH to 150-300 pg/mL 1
• Consider intravenous administration of calcitriol as it is more effective than oral administration 1
• For patients with elevated calcium or phosphorus, consider alternative vitamin D analogs such as paricalcitol or doxercalciferol 1
• Monitor calcium and phosphorus every 2 weeks for 1 month after initiating therapy or increasing dose, then monthly; check PTH monthly for 3 months, then quarterly 1
• Consider cinacalcet for dialysis patients with secondary hyperparathyroidism, starting at 30 mg once daily and titrating every 2-4 weeks to target iPTH levels of 150-300 pg/mL 4

Dose Adjustments for Vitamin D Therapy

• If PTH falls below target range: Hold vitamin D therapy until PTH rises above target, then resume at half the previous dose; if using lowest daily dose, switch to alternate-day dosing 1
• If calcium exceeds 9.5 mg/dL: Hold vitamin D therapy until calcium normalizes, then resume at half the previous dose 1
• If phosphorus exceeds 4.6 mg/dL: Hold vitamin D therapy, increase phosphate binders until phosphorus normalizes, then resume vitamin D 1

Management of Primary Hyperparathyroidism

• Consider parathyroidectomy for patients with severe hyperparathyroidism (persistent serum intact PTH >800 pg/mL) with hypercalcemia and/or hyperphosphatemia refractory to medical therapy 1, 2
• Surgical options include subtotal parathyroidectomy or total parathyroidectomy with parathyroid tissue autotransplantation 1, 2
• For patients who cannot undergo surgery, cinacalcet can be used starting at 30 mg twice daily, titrating every 2-4 weeks to normalize calcium levels 4
• Monitor serum calcium within 1 week after initiating or adjusting cinacalcet dose 4

Management of Adynamic Bone Disease

• For patients with adynamic bone disease (intact PTH <100 pg/mL in CKD Stage 5), allow PTH levels to rise to increase bone turnover 1
• Decrease doses of calcium-based phosphate binders and vitamin D or eliminate such therapy 1

Post-Parathyroidectomy Management

• Monitor ionized calcium every 4-6 hours for the first 48-72 hours after surgery, then twice daily until stable 5
• For hungry bone syndrome (severe hypocalcemia after parathyroidectomy):
  • Administer calcium gluconate infusion at 1-2 mg elemental calcium per kg body weight per hour 5
  • Transition to oral calcium carbonate 1-2 g three times daily when oral intake is possible 5
  • Consider calcitriol up to 2 μg/day to enhance intestinal calcium absorption 5

Important Monitoring Considerations

• Measure serum calcium and phosphorus within 1 week and intact PTH within 1-4 weeks after initiating or adjusting cinacalcet 4
• For patients on cinacalcet maintenance therapy, monitor serum calcium monthly for secondary hyperparathyroidism and every 2 months for primary hyperparathyroidism 4
• If calcium falls below 8.4 mg/dL on cinacalcet, increase calcium-containing phosphate binders and/or vitamin D sterols 4
• If calcium falls below 7.5 mg/dL or symptoms of hypocalcemia persist, withhold cinacalcet until calcium reaches 8 mg/dL, then restart at a lower dose 4

Pitfalls to Avoid

• Not assessing vitamin D status when interpreting PTH levels can lead to misdiagnosis 2
• Using different PTH assay generations without considering their varying sensitivity to PTH fragments can result in inaccurate diagnoses 2, 3
• Initiating vitamin D therapy in patients with rapidly worsening kidney function or those who are noncompliant with medications or follow-up 1
• Failing to monitor calcium and phosphorus levels closely when initiating or adjusting therapy 1, 4