A blood test that measures the level of parathyroid hormone secreted by the parathyroid glands in the neck. Used in the diagnosis of calcium metabolism and bone health disorders.
Indication
- Investigation of the cause of high or low blood calcium levels
- History of recurrent kidney stones
- Unexplained bone loss (osteoporosis) or bone pain
- Monitoring of secondary hyperparathyroidism in chronic kidney disease
- Evaluation in conjunction with vitamin D deficiency
- Suspected parathyroid adenoma in the neck region
- Pre- and postoperative evaluation in parathyroid surgery
Preparation
- The test is performed in the morning, preferably between 08:00 and 10:00
- 8 hours of fasting is generally required (water is allowed)
- Calcium, vitamin D and phosphorus levels are usually tested in the same sample
- Use of calcium, vitamin D and diuretic medications should be reported to the doctor
- Vigorous exercise should be avoided for 24 hours before the test
How it's performed
- The patient is rested in a sitting or supine position
- About 3-5 mL of blood is drawn from the arm into a vacuum tube
- Calcium, phosphorus, 25-OH vitamin D and creatinine samples are collected at the same time
- The sample is transported to the laboratory under cold-chain conditions
- Intact PTH level is measured by immunoassay
- The result is reported in pg/mL and interpreted together with calcium and vitamin D
Post-procedure
- Results are usually available the same day or the next business day
- High PTH with high calcium prompts evaluation for primary hyperparathyroidism
- High PTH with low calcium prompts evaluation for vitamin D deficiency or chronic kidney disease
- When indicated, neck ultrasound or parathyroid scintigraphy is planned
- Results are interpreted by an endocrinology or nephrology specialist
Risks
- Temporary bruising or pain at the blood draw site
- Very rare infection
- Brief dizziness due to a vasovagal response
- Risk of falsely low result if the sample is not stored correctly
FAQ
Can PTH be interpreted on its own?
No. PTH is always evaluated together with calcium, phosphorus and vitamin D measured in the same blood sample.
Does an elevated PTH always require surgery?
No. Treatment depends on the cause. When the elevation is due to vitamin D deficiency, vitamin supplementation may be sufficient; in parathyroid adenoma, surgery may be considered.
Do I need to fast before the test?
Generally, 8 hours of fasting is recommended because calcium and phosphorus are measured from the same sample. You may drink water.
How long does it take to get the result?
In most laboratories the result is available the same day or by the next business day at the latest.
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