Description
The PTH-Related Peptide (PTHrP) test measures levels of a protein that behaves similarly to parathyroid hormone (PTH). PTHrP plays a role in calcium regulation by signaling bones, kidneys, and the intestines to release or retain calcium. Elevated PTHrP is most often associated with certain malignancies, particularly breast, lung, and kidney cancers, and can lead to hypercalcemia (high blood calcium), which can have serious health consequences if not addressed.
This test is often ordered when blood calcium levels are high but PTH is normal or low, helping differentiate the underlying cause of calcium imbalance.
Purpose of the Test
- Identify Humoral Hypercalcemia of Malignancy (HHM): Some tumors produce PTHrP, leading to elevated calcium without increased parathyroid activity.
- Differentiate Causes of Hypercalcemia: Distinguishes cancer-related hypercalcemia from primary hyperparathyroidism or vitamin D–related causes.
- Monitor Cancer Patients: Track changes in calcium regulation during cancer treatment or disease progression.
- Guide Treatment Decisions: Helps clinicians determine the best interventions to normalize calcium levels and prevent complications.
Clinical Relevance
- High PTHrP Levels
- Often indicate a malignancy-related cause of high calcium.
- Can cause muscle weakness, fatigue, confusion, excessive thirst, frequent urination, kidney stones, or cardiac arrhythmias if untreated.
- Normal PTHrP Levels
- Suggest calcium imbalance may be due to primary hyperparathyroidism, vitamin D toxicity, kidney disease, or other metabolic disorders.
- Monitoring & Management
- Used alongside calcium, PTH, and vitamin D tests for a full picture of calcium homeostasis.
- Important for preventing hypercalcemic crises, which can be life-threatening.
Symptoms That May Prompt Testing
- Unexplained high blood calcium
- Fatigue or muscle weakness
- Bone pain or fractures
- Excessive thirst and urination
- Nausea, vomiting, or constipation
- Confusion or cognitive changes
Test Details
- Sample Type: Blood
- Fasting Required: No
