Parathyroid Hormone
The hormone that controls blood calcium levels, acting on bone, kidneys and vitamin D activation.
| Typical reference range | 16–77 pg/mL |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
Parathyroid hormone is released by four small glands behind the thyroid when blood calcium falls. It releases calcium from bone, increases calcium reabsorption by the kidneys and stimulates activation of vitamin D.
Why it matters
PTH, interpreted together with calcium, distinguishes parathyroid disorders from other causes of abnormal calcium, and reveals secondary hyperparathyroidism from vitamin D deficiency or kidney disease, which can weaken bones.
What a high result can mean
High PTH with high calcium suggests primary hyperparathyroidism. High PTH with normal or low calcium suggests secondary hyperparathyroidism from vitamin D deficiency, low calcium intake, kidney disease or malabsorption. Lithium and thiazides can also raise it.
What a low result can mean
Low PTH with high calcium suggests a non-parathyroid cause such as cancer, excess vitamin D or sarcoidosis. Low PTH with low calcium indicates hypoparathyroidism, often after neck surgery, or low magnesium.
What affects the result
Always interpret with simultaneous calcium, vitamin D, phosphorus and kidney function. PTH has a daily rhythm and is best drawn in the morning, fasting. Biotin can interfere with some assays.
Units and conversion
Usually reported in pg/mL.
- From ng/L: multiply by 1 to get pg/mL
- From pmol/L: multiply by 9.43 to get pg/mL
Also called on lab reports
PTH, PTH, Intact, Intact PTH, PTH Intact, Parathyroid Hormone, Intact, PTH, Intact and Calcium
Related tests: Muscle & Bone
This page is educational and does not replace advice from a healthcare professional.