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Parathyroid Hormone (PTH) Function: High & Low Levels

Written by Wendy Phillips, PhD (Biology) | Reviewed by Biljana Novkovic, PhD | Last updated:
Medically reviewed by
Evguenia Alechine, PhD (Biochemistry) | Written by Wendy Phillips, PhD (Biology) | Reviewed by Biljana Novkovic, PhD | Last updated:

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Hidden in the back of the thyroid gland are 4 small parathyroid glands that release parathyroid hormone (PTH), which is critical for maintaining mineral balance in the body. When blood PTH levels are high or low, symptoms can arise or just cause a general sense of feeling unwell. Read on to learn more about PTH and how high or low levels can affect your health.

What is Parathyroid Hormone (PTH)?

Parathyroid hormone (PTH) is produced by the parathyroid glands. Most people have 4 pea-sized parathyroid glands embedded in the back of the thyroid gland, but variations in their location and number sometimes occur.

PTH regulates calcium, phosphorus, and also magnesium levels in the blood.

Because calcium balance plays a critical role in many bodily functions, including muscle movement and nerve impulses, calcium levels are tightly controlled to stay within a narrow concentration range in the blood.

PTH’s main function is to increase calcium levels when they are too low. It triggers the release of calcium from bones to the blood, decreases the loss of calcium in the urine, and increases calcium absorption from food [1].

Measuring parathyroid hormone levels can help uncover the cause of improper calcium levels and can be used to monitor the progression of some diseases.

Increases Blood Calcium

1) Via Bones

Bones act as calcium reservoirs, releasing calcium into the bloodstream when blood levels are low and taking up calcium when they are high. PTH communicates to bone cells which action is needed [2].

Parathyroid glands have calcium sensors. When calcium is low, the glands release more PTH. High PTH levels signal the bones to release more calcium into the blood [2].

When calcium levels in the blood are high, parathyroid glands release less PTH. Low PTH levels signal bones to take up calcium from the blood [2].

2) Via Kidneys

As blood is filtered through the kidneys, some molecules are returned to the blood and some are removed from the body in the urine. Parathyroid hormone influences the net balance of how much calcium and phosphorus is removed and how much is retained during that process [3].

When PTH is high, the kidneys absorb less calcium. When PTH is low, more calcium is eliminated in the urine, decreasing the calcium concentration in blood [3].

3) Via Intestines

Parathyroid hormone triggers the kidneys to convert vitamin D from its inactive to its active form (1,25-dihydroxy vitamin D or calcitriol). In its active form, vitamin D increases the absorption of calcium in the intestines [4, 5, 6].

Higher PTH levels lead to an increase in active vitamin D, which leads to an increase in intestinal calcium absorption, which leads to a higher calcium concentration in the blood [5].


Calcitonin is produced in the thyroid gland and helps maintain calcium blood levels. If calcium levels are too high, then calcitonin reduces them [7].

Calcitonin is produced in response to high calcium levels in the blood [8].

Basically, calcitonin has the opposite effect of PTH. Both hormones are responsible for maintaining healthy levels of calcium in the blood [9].

Parathyroid Hormone Test

Parathyroid hormone level can be measured by a blood test, and it normally ranges between 10 to 65 ng/L [10].

Different testing methods may be used by different laboratories, which is why the normal ranges may vary.

Therefore, while labs will provide the range of normal values for their methodology, direct comparison of values from different labs may be inappropriate [11].

Normal Biological Variation

Normally, PTH is released both at low levels throughout the day and at pulses of higher levels a few times per hour [12].

An analysis of 3.6 million blood tests showed that both vitamin D and PTH levels vary seasonally. When vitamin D levels decrease, PTH levels increase, following about 4 weeks behind vitamin D levels [13].

On average, men’s vitamin D levels are lower and PTH levels are higher than women’s levels [13].

Parathyroid hormone levels can also increase during and following exercise, depending on its duration and intensity [14].

Levels May Differ Between Populations

In one study, Mexican- and African-Americans were found to have higher PTH than whites. However, both black and white Americans were found to have a higher incidence of primary hyperparathyroidism (abnormally high PTH) than Mexican-Americans in another study [15, 16].

Also, vitamin D deficiencies impacted PTH levels differently in African-Americans than in the other two groups. While PTH levels continued to decline with levels of vitamin D greater than 20 ng/ml in whites and Mexican-Americans, they did not follow the same pattern with vitamin D greater than 20 ng/ml in blacks [15].

Levels Are Higher with Obesity

As total body fat increases, parathyroid hormone levels increase. The effect of obesity on PTH levels is seen even when controlling for the decrease in vitamin D levels associated with more body fat [17].

Increasing waist size in women carries an increased risk of developing hyperparathyroidism (abnormally high PTH) [18].

One study found that both leptin and PTH levels increase with increasing body mass. However, it was only in people with higher leptin levels (greater than 10 ng/ml) that a decrease in vitamin D was associated with an increase in PTH. Leptin seems to affect PTH levels and both leptin and PTH regulate the conversion of vitamin D to its active form [19].

High Parathyroid Hormone (Hyperparathyroidism)

Hyperparathyroidism is the condition of having abnormally high blood parathyroid hormone levels.

High parathyroid hormone levels have been associated with the following symptoms and health problems:

  • Kidney disease [20]
  • Kidney stones [21]
  • Osteoporosis [22]
  • Bone, joint, or muscle pain [23]
  • High blood pressure [24, 25, 26]
  • Hardening of the arteries (arteriosclerosis) [27, 28]
  • Heart-related disorders [29, 30]
  • Colon polyps (adenomas) [31, 32]
  • Inflammation [33]
  • Fatigue [23]
  • Depression [34]
  • Brain fog [23]
  • Cystic fibrosis [35]
  • Liver disease [36]
  • Primary aldosteronism (high aldosterone levels) [30]

Causes of Abnormally High Parathyroid Hormone Levels

1) Dietary Deficiencies

Abnormally low levels of calcium in the blood increase parathyroid hormone levels. Dietary deficiencies in calcium or vitamin D are the most direct causes of low blood calcium levels [37].

Supplementation with vitamin D and K as well as calcium can decrease PTH levels and improve bone strength in women with osteoporosis [38].

2) Health Issues that Cause Low Calcium Levels

Chronic kidney disease can impair kidney function, which can decrease the amount of calcium reabsorbed by kidneys during blood filtration. The resulting low blood calcium levels signal the parathyroid glands to release more PTH, causing abnormally high levels of the hormone in the blood [39, 20].

Primary aldosteronism (high aldosterone levels) can cause high PTH levels. High aldosterone levels cause the kidneys to release more calcium into the urine, lowering blood calcium levels and triggering the parathyroid glands to release more PTH [30, 40, 41].

Poor absorption of nutrients by the intestines can lead to low blood calcium levels, which could trigger more PTH release [42].

3) Parathyroid Gland Malfunctioning

The most common problem with parathyroid glands is the excessive release of PTH despite normal or even high blood calcium levels. This is known as primary hyperparathyroidism.

Parathyroid gland malfunctions are most commonly caused by a benign tumor (adenoma). The second most common cause is increased cell growth in the parathyroid gland (hyperplasia). Cancer of the parathyroid glands is responsible for about 1% of cases [23].

4) Some Drugs

High parathyroid hormone levels can be a side effect of high dose lithium treatment for bipolar disorder [43].

Furosemide (Frusemide), a diuretic used to treat fluid buildup and high blood pressure, increases PTH levels [44].

5) Genes

Increased PTH levels are associated with genetic variations in or near genes involved in vitamin D production and calcium and phosphate transport, including these SNPs [45]:

Hyperparathyroidism has also been associated with mutations in:

How to Decrease Parathyroid Hormone Levels

If high PTH levels are caused by nutritional deficiencies, the levels may be brought back to normal values by taking calcium and vitamin D supplements.

However, high PTH is more often caused by parathyroid gland tumors or chronic kidney disease. In that case, the underlying condition needs treatment.

Ways to decrease PTH levels or reduce the risk of developing hyperparathyroidism include:

  • Calcium supplements [48]
  • Vitamin D supplements and sun exposure [49, 50]
  • Weight loss [18]
  • Exercise [51]
  • Reducing inflammation [33, 52].

Low Parathyroid Hormone (Hypoparathyroidism)

Hypoparathyroidism is the condition of having low or inappropriately normal blood parathyroid hormone levels.

If blood calcium levels are low, the parathyroid glands normally release extra PTH. So, PTH levels in the normal range are considered inappropriate when blood calcium levels remain low.

It is estimated that, in the US, 60,000 to 80,000 people have hypoparathyroidism [53].

Hypoparathyroidism usually leads to low calcium and high phosphate levels in the blood [54].

Causes of Low Parathyroid Hormone

1) Surgery

About 75% of hypoparathyroidism cases are the result of neck surgery, such as for removal of thyroid or parathyroid glands [55].

Hypoparathyroidism resulting from surgery can cause a quick drop in calcium levels that requires immediate attention. Generally, post-surgical hypoparathyroidism is defined as having blood calcium less than 8.0 mg/dL and PTH less than 15 ng/L [54].

About 75% of the hypoparathyroidism cases following surgery are transient (temporary) and PTH levels return to normal in less than 6 months [56].

Low vitamin D levels prior to surgery can increase the risk for post-surgical hypoparathyroidism. To minimize risk, it is recommended that pre-surgery vitamin D levels in the blood are at least 20 ng/dL [53].

2) Magnesium Imbalance

Both high and very low levels of magnesium decrease blood PTH levels [54].

3) Autoimmune Disorders

Hypoparathyroidism often occurs as a part of an autoimmune polyendocrine syndrome, which is a genetic disorder [57].

Apart from that, autoantibodies directed against a few parathyroid-related proteins have been identified in patients with hypoparathyroidism without other known causes, such as the calcium-sensing receptor (CaSR) and the NACHT leucine-rich-repeat protein 5 (NALP5) [57, 58].

4) Some Drugs

Digoxin, which is used to treat atrial fibrillation, decreases parathyroid hormone levels [59].

5) Genes

These genetic disorders and their related genes are associated with hypoparathyroidism [54]:

  • Autoimmune polyendocrinopathy syndrome type 1 (AIRE)
  • DiGeorge syndrome types 1 (TBX1) and 2 (NEBL)
  • Hypoparathyroidism-deafness-renal dysplasia syndrome (GATA3)
  • Kenny-Caffey syndrome type 1 (TBCE) and 2 (FAM111A)
  • CHARGE syndrome (CHD7, SEMA3E)
  • Bartter syndrome, type 5 (CASR)

Mutations in these genes have been associated with hypoparathyroidism [60, 61, 62]:

Treatment of Hypoparathyroidism

Hypoparathyroidism is most commonly treated with calcium (1,000 to 9,000 mg/day) and vitamin D (0.25 to 2.0 ug/day of calcitriol) supplements. The goal is to maintain blood calcium levels at 8.0 to 9.0 mg/dL while avoiding high levels of calcium in the urine [53].

A synthetic parathyroid hormone (Natpara) was approved by the FDA as a treatment in 2015. However, long-term complications from its use are still being evaluated [63, 53].

Health Issues Associated with Hypoparathyroidism

The low calcium levels caused by hypoparathyroidism most commonly lead to problems with muscles and the nervous system [54].

The high calcium intake used to treat low PTH levels can cause kidney stones and increase the risk of developing chronic kidney disease [54].

Bone mass density is usually higher in patients with chronic hypothyroidism. Whether that is due to treatment with calcium and vitamin D supplements or low PTH levels reducing bone restructuring, or whether it is a combination of the two is unclear [54].

Many patients with hypoparathyroidism report a reduced quality of life, including fatigue, depression, anxiety, and cognitive difficulties [53].

Health issues associated with hypoparathyroidism may result from low calcium levels or from treatment with calcium supplements. They include [54, 64]:

  • Fatigue
  • Muscle cramps
  • Heart disease
  • Seizures
  • Psychiatric disorders
  • Infections requiring hospitalization
  • Kidney disorders
  • Cataracts
  • Bronchial spasms
  • Bone fractures in arms
  • Calcium deposits in the brain (basal ganglia calcification)

How to Increase Parathyroid Hormone Levels

Make sure your magnesium levels are in balance. If they are on the low end, you may want to take magnesium supplements [54].

Use of Parathyroid Hormone to Treat Osteoporosis

Because parathyroid hormone is a key controller of bone building, it is an important factor in many bone disorders.

A synthetic parathyroid hormone analog (teriparatide) is used for treating severe osteoporosis. It is effective at building bone when given in intermittent, low doses [65, 66, 67].

In 2017, another parathyroid hormone-like medication, abaloparatide, was approved by the FDA for treating severe osteoporosis [68, 69].

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