What does a Parathyroid Hormone (PTH) level of 314 signify?

What Does a PTH Level of 314 pg/mL Signify?

A PTH level of 314 pg/mL indicates significant parathyroid hormone elevation that requires immediate investigation to distinguish between primary hyperparathyroidism (if calcium is elevated), secondary hyperparathyroidism (if calcium is normal/low with kidney disease or vitamin D deficiency), or tertiary hyperparathyroidism (if hypercalcemic after long-standing kidney disease). 1

Immediate Diagnostic Algorithm

Step 1: Measure Serum Calcium Simultaneously

• If calcium is elevated or high-normal: This confirms primary hyperparathyroidism, where PTH of 314 pg/mL with hypercalcemia represents inappropriately elevated PTH that should be suppressed 1
• If calcium is normal or low: This suggests secondary hyperparathyroidism, commonly from chronic kidney disease (CKD) or vitamin D deficiency 1
• If calcium is elevated with history of CKD: This indicates tertiary hyperparathyroidism, where autonomous PTH secretion persists despite correction of underlying kidney disease 2

Step 2: Assess Kidney Function and Vitamin D Status

• Measure serum creatinine and calculate GFR to evaluate for CKD 1
• Check 25-hydroxyvitamin D levels, as vitamin D deficiency can elevate PTH and complicate interpretation 1
• Measure serum phosphate (typically low in primary hyperparathyroidism, high in secondary hyperparathyroidism from CKD) 1

Clinical Context by Disease State

In CKD Patients (Secondary Hyperparathyroidism)

For patients with CKD and GFR <60 mL/min/1.73 m², a PTH of 314 pg/mL falls within acceptable ranges depending on CKD stage:

• CKD Stage 3-4: Target PTH is approximately 35-70 pg/mL (upper limit of normal), though modest elevations up to 2× normal may be acceptable 3, 4
• CKD Stage 5 (dialysis): Target PTH range is 150-300 pg/mL according to K/DOQI guidelines 3
  • PTH of 314 pg/mL is just above the upper target but not severely elevated
  • PTH >300 pg/mL may warrant adjustment of dialysate calcium or medical therapy 3
  • PTH >800-1000 pg/mL indicates severe disease requiring aggressive intervention 5

Critical point: In dialysis patients, PTH of 314 pg/mL represents mild elevation that may require monitoring and potential therapy adjustment, but does not indicate crisis-level hyperparathyroidism 3

In Primary Hyperparathyroidism

If calcium is elevated with PTH of 314 pg/mL:

• This confirms primary hyperparathyroidism with inappropriately elevated PTH 1
• Proceed with 24-hour urine calcium collection to assess stone risk 1
• Surgical referral is indicated if any of the following criteria are met 1:
  • Corrected calcium >1 mg/dL above upper limit of normal
  • Age <50 years
  • GFR <60 mL/min/1.73 m²
  • Osteoporosis (T-score ≤-2.5)
  • Nephrolithiasis or nephrocalcinosis
  • 24-hour urine calcium >400 mg/day

In Tertiary Hyperparathyroidism

If hypercalcemia persists after renal transplantation with PTH of 314 pg/mL:

• This represents tertiary hyperparathyroidism with autonomous parathyroid function 2
• Parathyroid glands have become resistant to normal feedback mechanisms 2
• Surgical parathyroidectomy is the primary treatment for persistent hypercalcemia 2

Key Diagnostic Pitfalls to Avoid

• Never interpret PTH without simultaneous calcium measurement - this is the most critical error that leads to misdiagnosis 1
• Always check vitamin D status - vitamin D deficiency can elevate PTH and mask the true diagnosis, potentially leading to unnecessary parathyroid surgery 1
• Use assay-specific reference ranges - different PTH assays measure different fragments and can yield significantly different values 1, 6
• Collect blood in EDTA tubes for most accurate PTH measurement 1
• Consider biotin interference - supplements can cause falsely low or high PTH depending on assay design 1

Severity Assessment

PTH of 314 pg/mL represents:

• Mild-to-moderate elevation in the context of primary hyperparathyroidism 7, 8
• Slightly above target for dialysis patients (target 150-300 pg/mL) 3
• Not severe disease - severe hyperparathyroidism typically shows PTH >800-1000 pg/mL with bone pain, pathological fractures, and calcium-phosphate product >70 mg²/dL² 5

Immediate Next Steps

1. Obtain corrected serum calcium or ionized calcium 1
2. Measure 25-hydroxyvitamin D, serum phosphate, and creatinine 1
3. Calculate calcium-phosphate product if CKD is present 3
4. Determine if surgical criteria are met for primary hyperparathyroidism 1
5. Adjust dialysate calcium or initiate calcimimetic therapy if dialysis patient with PTH persistently >300 pg/mL 3, 9