Parathyroid Hormone: What It Is, Function & Normal Levels

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Parathyroid hormone (PTH) is a hormone your parathyroid glands release to control calcium levels in your blood. It also controls phosphorus and vitamin D levels. If your body has too much or too little parathyroid hormone, it can cause symptoms related to abnormal blood calcium levels.

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Parathyroid hormone (PTH) is a hormone that your parathyroid glands make and release to control the level of calcium in your blood, not your bones.

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Calcium is one of the most important and common minerals in your body. PTH also helps control the levels of phosphorus (a mineral) and vitamin D (a hormone) in your blood and bones.

Your hormones are chemical messengers that work hard behind the scenes to keep you healthy. And parathyroid hormone is no different. It keeps your blood calcium levels in check so your nerves, muscles and heart can function properly.

Your parathyroid gland releases parathyroid hormone (PTH) when your body detects low calcium levels in your blood. These glands are embedded in the back of your thyroid.

PTH regulates calcium levels in your blood by affecting the following parts of your body:

Bones. PTH triggers the release of small amounts of calcium from your bones into your bloodstream.
Kidneys. PTH enables the production of active vitamin D (calcitriol) in your kidneys. PTH also signals your kidneys to keep calcium in your body rather than flushing it out through your pee.
Small intestine. PTH signals your small intestine to absorb more calcium from the food you eat.

Your body controls your parathyroid hormone levels by identifying how much calcium is in your blood. This is known as a feedback loop. In other words, low blood calcium levels trigger parathyroid hormone release. High blood calcium levels prevent your glands from releasing PTH.

But sometimes, an issue with your parathyroid glands can cause them to release too much or too little PTH, regardless of the feedback loop.

When your parathyroid hormone levels are off balance, it causes certain health conditions.

High PTH levels (hyperparathyroidism) cause:

High blood calcium levels (hypercalcemia)
Low levels of phosphorous in your blood (hypophosphatemia)

Hyperparathyroidism has several possible causes. Some causes include parathyroid cancer, parathyroid adenoma and kidney disease.

Low PTH levels (hypoparathyroidism) cause:

Low blood calcium levels (hypocalcemia)
High levels of phosphorous in your blood (hyperphosphatemia)

Hypoparathyroidism is rare. About 3 out of 4 cases (75%) are from accidental damage to your parathyroid glands from neck or thyroid surgery. Certain genetic and autoimmune conditions can cause it as well.

PTH mainly controls the amount of calcium in your blood. So, the symptoms of low or high PTH levels are actually the symptoms of low or high blood calcium levels.

Low blood calcium can cause symptoms like:

Brain fog or confusion
Dry skin and brittle nails
Muscle cramps
Tingling in your lips, fingers or feet

High blood calcium can cause symptoms like:

Fatigue
Headaches
Joint pain and bone pain
Peeing more frequently and being thirsty

You should see your healthcare provider if you have symptoms of low or high blood calcium levels.

Your healthcare provider can check your parathyroid hormone levels with a blood test. Healthcare providers and laboratories call this test “PTH, intact.”

In general, the normal range for a PTH blood test is 15 to 65 picograms per milliliter (pg/mL). A picogram is one-trillionth of a gram.

Normal ranges for parathyroid hormone levels can vary from lab to lab. Always reference the lab’s normal range on your blood test report.

If you need a PTH level test, your healthcare provider will assess your result. They’ll let you know if you need further testing.

Parathyroid hormone is an important hormone that’s in charge of managing your blood calcium levels. If you’re experiencing symptoms of hypercalcemia or hypocalcemia, like issues with your muscles and mental function, it’s important to contact your healthcare provider. They can run some simple tests to see if your parathyroid hormone levels are the culprit.

Learn more about the Health Library and our editorial process.

Cleveland Clinic’s health articles are based on evidence-backed information and review by medical professionals to ensure accuracy, reliability and up-to-date clinical standards.

Khan M, Jose A, Sharma S. Physiology, Parathyroid Hormone (https://www.ncbi.nlm.nih.gov/books/NBK499940/). 2022 Oct 29. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan. Accessed 2/17/2025.
Society for Endocrinology. Parathyroid Hormone (https://www.yourhormones.info/hormones/parathyroid-hormone/). Last reviewed 12/2020. Accessed 2/17/2025.
Society for Endocrinology. Vitamin D (https://www.yourhormones.info/hormones/vitamin-d/). Last reviewed 11/2021. Accessed 2/17/2025.

Cleveland Clinic treats all parathyroid diseases, including cancer, and their side effects. We’ll create a personalized treatment plan that meets your needs.

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Peptide Therapy Guide Editorial Team