Parathyroid hormone, intact (PTH)

What it measures

PTH is secreted by the parathyroid glands to raise blood calcium. It is always interpreted with calcium to investigate hypercalcaemia, hypocalcaemia, kidney bone disease and vitamin D deficiency.

Specimen and preparation

• Specimen: EDTA plasma (more stable) or serum
• Tube: Lavender top
• Preparation: Separate promptly; collect calcium at the same time.

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Primary hyperparathyroidism
• Secondary hyperparathyroidism (CKD, vitamin D deficiency)
• Tertiary hyperparathyroidism
• Lithium therapy
• Low calcium intake

Causes of low values

• Hypoparathyroidism (post-surgical, autoimmune)
• Hypercalcaemia of malignancy
• Vitamin D toxicity
• Severe hypomagnesaemia
• Sarcoidosis

Method

Two-site chemiluminescent immunoassay

Good to know

High calcium with high or inappropriately normal PTH indicates primary hyperparathyroidism.

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