Parathyroid hormone (PTH) is produced by the four parathyroid glands located behind the thyroid gland. Its primary role is to regulate calcium and phosphate balance by stimulating bone resorption to release calcium, increasing renal calcium reabsorption, reducing phosphate reabsorption by the kidney, and stimulating activation of vitamin D to enhance intestinal calcium absorption.
PTH is measured when abnormal calcium levels are found on blood testing, when bone density loss needs investigation, or when symptoms of hypercalcaemia or hypocalcaemia are present. Together with calcium and vitamin D levels, PTH provides the key information for diagnosing the cause of calcium disorders including primary hyperparathyroidism, vitamin D deficiency, and hypoparathyroidism.
FAQs
What is primary hyperparathyroidism?
Primary hyperparathyroidism is caused by overactive parathyroid glands (usually a single benign adenoma) producing excess PTH autonomously. It causes elevated or high-normal calcium, kidney stones, bone loss, and often no symptoms for years. Parathyroidectomy is curative.
Can vitamin D deficiency cause elevated PTH?
Yes. Vitamin D deficiency reduces calcium absorption, which triggers compensatory PTH secretion (secondary hyperparathyroidism). This is very common and resolves with vitamin D supplementation. It is the most common cause of elevated PTH in Australia.
How does CKD affect PTH?
Chronic kidney disease causes phosphate retention, reduced vitamin D activation, and hypocalcaemia, all of which stimulate PTH. Progressive secondary hyperparathyroidism accelerates bone loss and cardiovascular calcification in CKD, requiring active management.
When should PTH be collected?
PTH is ideally collected fasting in the morning (before 10am) for most consistent results. It degrades rapidly after collection and requires specific laboratory handling to ensure accurate measurement.
