How often should parathyroid hormone (PTH) levels be checked?

From the Guidelines

Parathyroid hormone (PTH) levels should be checked at intervals based on the presence and magnitude of abnormalities, and the rate of progression of chronic kidney disease (CKD), with specific monitoring intervals recommended for different CKD stages, such as every 6-12 months for CKD G1T-G3bT and every 3-6 months for CKD G4T. The frequency of monitoring PTH levels can vary depending on the patient's condition and stage of CKD. For patients with CKD G1T-G3bT, PTH levels should be checked once, with subsequent intervals depending on baseline level and CKD progression, while for CKD G4T, PTH levels should be checked every 6-12 months 1. In CKD G5T, PTH levels should be checked every 3-6 months. It is also important to consider the type of PTH assay used, as different generations of assays can recognize different fragments of PTH, which can affect clinical decisions 1.

Key Considerations for PTH Monitoring

• The presence and magnitude of abnormalities in serum calcium, phosphate, and PTH levels
• The rate of progression of CKD
• The type of PTH assay used
• The patient's response to treatment and any changes in their condition

Monitoring Intervals for Different CKD Stages

• CKD G1T-G3bT: every 6-12 months
• CKD G4T: every 3-6 months
• CKD G5T: every 3-6 months
• Patients with unstable PTH levels or those undergoing active treatment adjustments: every 1-3 months

Additional Recommendations

• PTH testing should be accompanied by calcium, phosphorus, and vitamin D measurements for comprehensive evaluation
• The timing of blood draws matters, with PTH having a diurnal variation with higher levels in the morning, so consistent timing helps with result interpretation
• Patients starting medications that affect calcium metabolism should have PTH measured 2-4 weeks after initiation or dose changes 1.

From the FDA Drug Label

1. 3 Laboratory Tests During the initial dosing or following any dose adjustment of medication, serum calcium, serum phosphorus, and serum or plasma iPTH should be monitored at least every two weeks for 3 months, then monthly for 3 months, and every 3 months thereafter.

Monitoring of PTH levels should be done:

• At least every two weeks for 3 months after initial dosing or dose adjustment
• Monthly for 3 months thereafter
• Every 3 months after that 2

From the Research

Parathyroid Hormone (PTH) Monitoring Frequency

The frequency of parathyroid hormone (PTH) monitoring can vary depending on the patient's condition and treatment.

• According to a study published in 2011 3, increasing the frequency of PTH monitoring from quarterly to monthly was associated with a significant increase in the percentage of patients reaching target PTH values.
• The study found that monthly PTH monitoring resulted in a higher percentage of patients with PTH levels within the target range of 150-300 pg/ml, compared to quarterly monitoring.
• Another study published in 2015 4 found that paricalcitol was effective in reducing PTH levels in kidney transplant recipients with secondary hyperparathyroidism, with significant reductions in PTH levels observed at 6,12, and 24 months.

Factors Influencing PTH Monitoring Frequency

Several factors can influence the frequency of PTH monitoring, including:

• Patient's response to treatment: Studies have shown that patients who respond well to treatment may require less frequent PTH monitoring 5, 6.
• Severity of secondary hyperparathyroidism: Patients with severe secondary hyperparathyroidism may require more frequent PTH monitoring to ensure that their PTH levels are within the target range 6, 7.
• Use of medications: The use of medications such as calcitriol, cinacalcet, and paricalcitol can affect PTH levels and may require more frequent monitoring 4, 6, 7.

Recommendations for PTH Monitoring

Based on the available evidence, it is recommended that:

• PTH levels be monitored monthly in patients with secondary hyperparathyroidism who are receiving treatment 3.
• The frequency of PTH monitoring be adjusted based on the patient's response to treatment and the severity of their secondary hyperparathyroidism 5, 6.
• Patients who are receiving medications that affect PTH levels be monitored more frequently to ensure that their PTH levels are within the target range 4, 6, 7.