From the Guidelines
Parathyroid hormone (PTH) levels should be checked when evaluating calcium metabolism disorders, particularly when abnormal serum calcium levels are detected, as well as in patients with kidney disease to diagnose secondary hyperparathyroidism, according to the most recent guidelines 1.
Indications for PTH Level Check
- Evaluating calcium metabolism disorders, particularly when abnormal serum calcium levels are detected
- Diagnosing secondary hyperparathyroidism in patients with kidney disease
- Assessing parathyroid gland function in patients with hypocalcemia (low calcium)
- Evaluating patients with osteoporosis or unexplained bone fractures
- Evaluating patients with kidney stones
Importance of PTH Measurement
PTH is the primary hormone regulating calcium homeostasis in the body, and its measurement is essential for diagnosing and managing various calcium metabolism disorders. The relationship between PTH and serum calcium levels provides crucial diagnostic information, such as high PTH with high calcium suggesting primary hyperparathyroidism, while high PTH with low calcium indicates a compensatory response to hypocalcemia.
Clinical Guidelines
The Kidney Disease: Improving Global Outcomes (KDIGO) 2017 clinical practice guideline update recommends measuring PTH levels in patients with chronic kidney disease (CKD) to diagnose and manage secondary hyperparathyroidism 1. The guideline suggests that patients with CKD G3a to G5 not on dialysis should have their PTH levels measured and evaluated for modifiable factors, including hyperphosphatemia, hypocalcemia, high phosphate intake, and vitamin D deficiency.
Assay Generation and Standardization
Different generations of PTH assays may recognize different fragments of PTH, which can affect the accuracy of PTH measurements 1. Therefore, it is essential to consider the assay generation and standardization when interpreting PTH results. However, the most recent guidelines do not provide specific recommendations on the use of different assay generations.
From the FDA Drug Label
iPTH levels should be measured no earlier than 12 hours after most recent dose.
- When to check a PTH level: PTH levels should be measured no earlier than 12 hours after the most recent dose of cinacalcet.
- Key consideration: The timing of PTH level measurement is crucial to ensure accurate results, and it should be done at least 12 hours after the last dose of cinacalcet 2.
From the Research
When to Check PTH Levels
- PTH levels should be checked in patients with chronic kidney disease (CKD) as secondary hyperparathyroidism is a common complication of CKD 3.
- Patients with primary hyperparathyroidism (PHPT) should have their PTH levels checked, especially if they are experiencing symptoms such as cognitive impairment, changes in sensorium, proximal muscle weakness, nausea and vomiting, constipation, and severe dehydration 4.
- PTH levels should be monitored in peritoneal dialysis patients as abnormal levels are associated with higher mortality rates 5.
- In hemodialysis patients, PTH levels should be checked regularly to monitor the effects of treatment on secondary hyperparathyroidism, and changes in phosphorus, calcium, and gender should be taken into account 6.
- Patients with PHPT and a low calcium intake may benefit from calcium supplementation, and PTH levels should be monitored to assess the effects of supplementation 7.
Factors Affecting PTH Levels
- Phosphorus levels: changes in serum phosphorus are significantly associated with changes in PTH levels 6.
- Calcium levels: changes in serum calcium are associated with changes in PTH levels, and calcium supplementation may affect PTH levels 6, 7.
- Gender: gender is a significant factor in the association between PTH levels and other biochemical variables 6.
- Kidney function: reduced kidney function is prevalent in patients with secondary hyperparathyroidism and PHPT 3, 4.
- Age: older patients with PHPT may be more likely to experience symptoms and have higher PTH levels 4.