Parathyroid Hormone (PTH) Test: Normal Range Explained

What Is Parathyroid Hormone?

PTH is produced by four small parathyroid glands in your neck. It regulates calcium, phosphorus and vitamin D levels in your blood and bones.

Normal PTH Range

What High PTH Means

What Low PTH Means

Hypoparathyroidism can result from gland damage during neck surgery, autoimmune disease or genetic conditions, leading to low calcium and symptoms like muscle cramps and tingling.

Symptoms of Abnormal PTH

• Bone pain or fractures
• Kidney stones
• Fatigue and weakness
• Muscle cramps or tingling (low calcium)
• Excessive thirst and urination (high calcium)

Frequently Asked Questions

Interpreting PTH alongside calcium

PTH is almost never interpreted alone: it only becomes meaningful when read together with the calcium level taken at the same time. Four broad patterns are recognised, and each points in a different direction.

High calcium with high or inappropriately normal PTH indicates primary hyperparathyroidism, usually from a benign parathyroid adenoma. High calcium with suppressed PTH suggests a non-parathyroid cause such as malignancy. Low calcium with high PTH is the expected compensatory picture in vitamin D deficiency or chronic kidney disease. Low calcium with low PTH points to hypoparathyroidism, often following thyroid or parathyroid surgery.

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

1. Primary Hyperparathyroidism. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK441895

References

Sources cited on this page. PubMed links open the original abstract.

1. Bilezikian JP, Brandi ML, Eastell R, et al. Guidelines for the management of asymptomatic primary hyperparathyroidism: fourth international workshop. J Clin Endocrinol Metab. 2014;99(10):3561–3569. PMID 24915830 · doi:10.1210/jc.2014-1413

The PTH-calcium relationship – the central regulating axis

Parathyroid hormone (PTH) and calcium are linked by a direct feedback loop: when blood calcium falls, parathyroid glands secrete PTH within seconds; when calcium rises, PTH is suppressed. This relationship is the key to interpreting any PTH result – the calcium level must be interpreted simultaneously:

• High PTH + high calcium = primary hyperparathyroidism (usually a single benign parathyroid adenoma secreting PTH autonomously, ignoring the normal feedback signal). This is the most common cause of hypercalcaemia in outpatients – asymptomatic hypercalcaemia found incidentally on routine blood tests is primary HPT until proven otherwise.
• High PTH + low or normal calcium = secondary hyperparathyroidism (the gland is working normally but being overstimulated by a chronically low calcium – most commonly in vitamin D deficiency, chronic kidney disease, or malabsorption). The parathyroids are responding appropriately to a deficiency, not behaving autonomously.
• High PTH + low calcium (after years of secondary HPT) = tertiary hyperparathyroidism (the glands have become autonomously hyperactive after years of stimulation – seen in long-standing CKD, particularly post-kidney transplant).
• Low PTH + high calcium = PTH-independent hypercalcaemia – the hypercalcaemia is coming from elsewhere: malignancy (PTHrP – PTH-related protein – from squamous cell lung cancer, renal cell cancer), vitamin D toxicity, sarcoidosis, or immobilisation. The suppressed PTH is appropriate – the parathyroids are working correctly but the high calcium is arising from a non-PTH source.

Primary hyperparathyroidism – management decisions

The majority of people with primary hyperparathyroidism found incidentally have only mildly elevated calcium and are asymptomatic. The decision to operate (parathyroidectomy – curative surgery) versus observe depends on whether any of the following criteria are met (per international consensus guidelines):

• Corrected calcium more than 0.25 mmol/L above the upper limit of normal
• eGFR below 60 mL/min/1.73m²
• DXA T-score below −2.5 at any site, or vertebral fracture on imaging
• Age below 50
• 24-hour urine calcium above 10 mmol/day (increasing stone risk)

Parathyroidectomy is recommended in symptomatic patients regardless of calcium level. Preoperative imaging (sestamibi parathyroid scan, 4DCT, or ultrasound) localises the adenoma to guide minimally invasive surgery – which is now the standard approach with 95% cure rates and very low complication rates.