PTH (Parathyroid Hormone)
Definition
PTH is produced by the four pea-sized parathyroid glands located in the neck. It is the chemical messenger that regulates the calcium level in the blood. When calcium falls, PTH is released and restores the balance in the following ways: it causes calcium to be released from the bones, increases absorption from the intestine, and helps the kidneys retain calcium.
Purpose
To determine whether abnormal blood calcium is of parathyroid origin, to monitor chronic kidney disease, to investigate severe osteoporosis, and to confirm treatment effectiveness in known parathyroid disease.
Results
PTH is not interpreted on its own but together with calcium:
| PTH | Calcium | Interpretation |
|---|---|---|
| High | High | Primary hyperparathyroidism (often an adenoma) |
| High | Low | Secondary hyperparathyroidism (external cause, e.g. vitamin D deficiency) |
| Low | Low | Hypoparathyroidism (the glands cannot produce enough PTH) |
Normal Values
Laboratory-specific.
Risks and Limitations
Results must be evaluated together with the calcium level and other tests. A PTH value cannot be interpreted on its own.