Parathyroid Hormone (PTH) Test: Levels & Causes

What Is Parathyroid Hormone (PTH)?

Parathyroid hormone (PTH) is a key regulator of calcium and phosphate balance in your body. Produced by four tiny glands behind your thyroid, this hormone acts like a thermostat—raising blood calcium when levels dip too low and lowering it when they climb too high. In my clinic, I often see patients who have been struggling with vague symptoms like muscle cramps, tingling fingers, or persistent bone pain, and a PTH test uncovers the root cause.

Why Is a PTH Blood Test Ordered?

Your doctor might check PTH if routine blood work shows abnormal calcium levels, or if you have symptoms of kidney stones, osteoporosis, or unexplained fractures. It is also used to monitor chronic kidney disease, after parathyroid gland surgery, or when vitamin D deficiency is suspected. The test is almost always interpreted alongside serum calcium, phosphate, and vitamin D (25-OH) levels.

Normal PTH Reference Ranges

Reference values vary slightly between laboratories, but the typical adult range is 10–65 pg/mL (1.1–6.9 pmol/L). Children and older adults may have slightly different norms. Below is a general guide:

What Does a High PTH Level Mean?

Elevated PTH (hyperparathyroidism) may be primary (a benign parathyroid adenoma) or secondary (due to low calcium, low vitamin D, or kidney failure). Common symptoms include fatigue, frequent urination, kidney stones, and bone thinning. In my practice, I often reassure patients that primary hyperparathyroidism is very treatable, often with minimally invasive surgery.

What Does a Low PTH Level Mean?

Low PTH (hypoparathyroidism) is less common and usually occurs after thyroid or parathyroid surgery, or from autoimmune destruction. Symptoms include tingling in the hands and feet, muscle cramps, and seizures. Treatment involves calcium and vitamin D supplements.

PTH and Vitamin D: A Critical Partnership

Vitamin D helps your gut absorb calcium; when it is deficient, PTH rises to pull calcium from your bones. This is why I always check both PTH and vitamin D in patients with osteoporosis or unexplained muscle aches. Correcting vitamin D deficiency often brings PTH back into the normal range.

PTH in Kidney Disease

Chronic kidney disease disrupts the balance of phosphate and calcium. The kidneys cannot activate vitamin D properly, leading to secondary hyperparathyroidism. Elevated PTH in CKD is a marker of bone disease (renal osteodystrophy) and requires careful management with phosphate binders, active vitamin D, or calcimimetics.

PTH During Pregnancy

During pregnancy, calcium demands increase for fetal bone development. PTH levels typically rise slightly, especially in the third trimester. This is a normal physiological adaptation. However, very high PTH with severe symptoms warrants further evaluation for pre-existing parathyroid disease.

PTH in Osteoporosis

In osteoporosis, the balance between bone formation and resorption is tilted. PTH plays a dual role—chronically high levels can accelerate bone loss, while intermittent low-dose PTH analogues (like teriparatide) actually stimulate new bone formation. Your doctor may use the PTH test to guide therapy.

How Is PTH Measured?

A simple blood draw is all that is needed. Fasting is often recommended, but not always required. Because PTH is unstable, the sample must be processed quickly—usually on ice. Results are typically available within 24 hours.