What to check for elevated Parathyroid Hormone (PTH) levels?

From the Guidelines

To check for elevated parathyroid hormone (PTH) levels, you should get a blood test that specifically measures intact PTH along with serum calcium levels, as this is crucial for identifying patients with normocalcemic primary hyperparathyroidism and for distinguishing between different causes of hypercalcemia 1. When ordering this test, it's essential to also check calcium, phosphorus, vitamin D (25-hydroxyvitamin D), and kidney function tests (BUN and creatinine) simultaneously to properly interpret the results.

• Normal PTH levels typically range from 10-65 pg/mL, though reference ranges may vary slightly between laboratories.
• Elevated PTH levels may indicate primary hyperparathyroidism (when calcium is also high), secondary hyperparathyroidism (often due to vitamin D deficiency or kidney disease), or other conditions affecting calcium metabolism. The test requires a simple blood draw, usually performed after fasting for 8-12 hours, and results are typically available within a few days. If elevated PTH is found, your doctor will likely recommend additional tests such as bone density scans, 24-hour urine calcium collection, or imaging studies to evaluate the parathyroid glands depending on your specific clinical situation, as accurate measurement of PTH is important for establishing the diagnosis and guiding treatment 1. It's also important to note that different generations of PTH assays may give different results, and the choice of assay can affect clinical decisions, particularly in patients with chronic kidney disease or those who have undergone bariatric surgery 1. In patients with severe secondary hyperparathyroidism, PTH levels may exceed 1,000 pg/mL, and treatment with vitamin D sterols may require larger doses and longer treatment periods 1.

From the FDA Drug Label

At study entry, 66% of the patients were receiving vitamin D sterols and 93% were receiving phosphate binders. Cinacalcet (or placebo) was initiated at a dose of 30 mg once daily and titrated every 3 or 4 weeks to a maximum dose of 180 mg once daily to achieve an iPTH of ≤ 250 pg/mL The dose was not increased if a patient had any of the following: iPTH ≤ 200 pg/mL, serum calcium < 7.8 mg/dL, or any symptoms of hypocalcemia.

To check for elevated Parathyroid Hormone (PTH) levels, the following should be monitored:

• iPTH levels: Target is ≤ 250 pg/mL
• Serum calcium levels: Should be ≥ 7.8 mg/dL to avoid hypocalcemia
• Symptoms of hypocalcemia: Should be monitored to avoid increasing the dose unnecessarily 2

From the Research

Elevated Parathyroid Hormone (PTH) Levels

To check for elevated PTH levels, several factors and conditions should be considered:

• Secondary hyperparathyroidism (SHPT) causes, such as vitamin D deficiency, low calcium intake, impaired renal function, malabsorptions, and certain medications like lithium salts and antiresorptive osteoporosis therapies 3
• Normocalcemic primary hyperparathyroidism (PHPT) diagnosis, which may involve a calcium load test to assess PTH response to increased calcemia 3
• Hypercalciuria and renal calcium leak, which can be evaluated using a thiazide challenge test to differentiate SHPT from normocalcemic PHPT 3
• Postoperative PTH levels after parathyroidectomy for primary hyperparathyroidism, which may be elevated in some patients despite normal calcium levels 4, 5, 6
• Potential etiologies for persistent PTH elevation, including bone hunger, vitamin D deficiency, inadequate calcium intake or absorption, reduced peripheral sensitivity to PTH, underlying chronic kidney disease, and/or a renal leak of calcium 5

Diagnostic Approach

The diagnostic approach for elevated PTH levels involves:

• Ruling out causes of SHPT, such as vitamin D deficiency and impaired renal function 3
• Evaluating serum calcium, phosphorus, and vitamin D levels to assess mineral metabolism 7, 3
• Assessing renal function and urine calcium excretion to identify potential renal causes of PTH elevation 3, 5
• Considering a calcium load test or thiazide challenge test to diagnose normocalcemic PHPT or SHPT due to a renal calcium leak 3

Monitoring and Follow-up

Patients with elevated PTH levels after parathyroidectomy for primary hyperparathyroidism should be monitored over time for:

• Normalization of PTH levels, which may occur with calcium and vitamin D supplementation 5
• Recurrence of primary hyperparathyroidism, which may be indicated by persistent PTH elevation 6
• Potential complications, such as impaired renal function and hypercalciuria, which may be associated with elevated PTH levels 5, 6