The Parathyroid Glands and Laboratory Tests

The average person has four parathyroid glands. These glands are button-sized and are situated at the base of the throat near the thyroid gland. Parathyroid glands produce a hormone called parathyroid (PTH) that is responsible for regulating the quantity of calcium in the blood.

Calcium is a mineral that is essential in the formation of bones, teeth, clotting of blood, and proper functioning of the heart, nerves, and muscles. About 99% of the calcium in the human body is found in the bones and teeth, while the rest circulates in the blood. Some calcium is eliminated from the body every day through urine.

To regulate the amount of calcium in the blood, the parathyroid hormone acts as part of a feedback system that includes vitamin D, phosphorus (as phosphate), and calcium. Phosphorus is another mineral that collaborates with calcium in its numerous operations in the body. Most of it combines with calcium to assist in the formation of teeth and bones. Vitamin D boosts the absorption of phosphate and calcium in the digestive system.

The parathyroid glands’ role is to ensure that the amount of calcium in the blood remains within a specific range. As the amount of calcium in the blood reduces, the parathyroid glands produce and release PTH, which works to increase the amount of calcium in the blood in 3 ways:

PTH triggers the kidneys to reduce the removal of calcium through urine and increase the removal of phosphate through urine.

It acts on the kidneys to transform vitamin D from the inactive to the active state. This, in turn, increases the quantity of calcium absorbed from food in the digestive system.

It boosts the release of calcium from bones into the bloodstream.

As the amount of calcium in the blood gets higher, the production of PTH by the parathyroid glands reduces. This feedback system ensures a dynamic but relatively stable concentration of calcium in the blood.

Parathyroid illnesses are conditions that affect the quantity of PTH (parathyroid hormone) produced, which in turn affects the amount of calcium in the bloodstream.


Hyperparathyroidism is a condition characterized by the production of excess PTH by the parathyroid glands. It is divided into three groups: primary, secondary, and tertiary.

Primary hyperparathyroidism is a disease where the parathyroid glands are dysfunctional—the disease results in excess PTH in the blood as well as excess calcium in the blood. Since calcium is derived from the bones, they, in turn, become weak over time, increasing the risk of fractures.

About 85% of primary hyperparathyroidism cases are caused by a benign tumor (adenoma) in a single parathyroid gland. Less common causes are as a result of multiple adenomas or hyperplasia (an increase in the activity and size of 2 or more parathyroid glands). Very rare cases of the disease (less than 1%) are caused by parathyroid cancer, where tumors cause the production of excess PTH.

About 100,000 individuals in the U.S suffer from primary hyperparathyroidism each year. The disease is more common in individuals aged over 50 years and is more prevalent in women than men. In rare scenarios, the condition is caused by a genetic, endocrine syndrome (Men 1 or Men 2).

Secondary hyperparathyroidism is caused by low concentrations of calcium in the blood, which can happen due to the following:

  • Kidney failure: this can cause low amounts of active Vitamin D and elevated levels of phosphate, which lead to increased production of PTH.
  • Vitamin D deficiency.
  • Low calcium absorption caused by gastrointestinal disorders.
  • Tertiary hyperparathyroidism is rare and occurs when the main cause behind secondary hyperparathyroidism is fixed, but the parathyroid glands continue to over-produce PTH.


Hypoparathyroidism is a PTH deficiency, and it can be a temporary or permanent condition. Hypoparathyroidism is not as common as hyperparathyroidism. Regardless of the cause, individuals with hypoparathyroidism have an elevated blood phosphorus level and a lower blood calcium level that may be mild or severe.

The leading cause of this condition is the removal of the parathyroid glands during surgical procedures necessary for the treatment of other conditions. Parathyroid glands may need to be removed if you have cancer of the throat or thyroid cancer. Surgery may also be necessary when treating hyperparathyroidism caused by hyperplasia (increase in the activity and size of the parathyroid glands). About 3 or 3.5 glands are removed, and the remaining glands or part of a gland can be auto transplanted to an individual’s forearm. If the remaining gland does not work as expected, hypoparathyroidism may occur.

In some cases, it is caused by damage to all parathyroid glands by an autoimmune condition.

In rare cases, it is caused by a failure of the glands to develop correctly.

Temporary hypoparathyroidism may occur soon after undergoing treatment for hyperparathyroidism. This is known as hungry bone syndrome and happens when PTH decreases rapidly, and the bones are forced to seek calcium from the bloodstream. It can also be observed in newly born infants whose mothers have hyperparathyroidism.

Radiotherapy for cancer patients that affects the neck or face: Too much exposure to radiation can damage the parathyroid glands.

Low levels of magnesium in the blood: normal levels of magnesium are necessary for PTH production and release.

Signs and Symptoms

Signs and symptoms of parathyroid disease are closely related with those of an individual with a low blood calcium concentration (hypocalcemia) that occurs with hypoparathyroidism or high blood calcium concentration (hypercalcemia) that occurs with hyperparathyroidism.

Some examples include:

  • Low calcium (hypothyroidism)
  • Depression or anxiety
  • Dry skin, brittle nails
  • Hair loss
  • Painful menstrual periods
  • Fatigue
  • Numbness and tingling sensations in the lips, toes, and fingers
  • Muscle cramps or twitching
  • Abdominal pain
  • High calcium (hyperparathyroidism):
  • Depression
  • Constipation
  • Kidney stones (excess calcium in the urine can crystalize and form stones)
  • Bone pain and fragile bones
  • Frequent urination
  • Feeling very thirsty
  • Abdominal pain, loss of appetite, nausea,
  • Fatigue

Many people with parathyroid disease are diagnosed at an early stage with minimal or no complications, but others may experience mild to severe complications before seeking medical care.


Testing is done to monitor, diagnose, and detect parathyroid diseases. The first sign of parathyroid disease may be an irregular blood calcium result on a routine blood test (like a CMP- Comprehensive Metabolic Panel). Some of the tests used to diagnose the parathyroid glands are noted below.

Some of the test results for patients with hyperparathyroidism include:

Calcium – elevated calcium levels, although many conditions may cause increased levels of calcium in the blood, so the test must be repeated multiple times to ascertain the cause.

PTH (parathyroid hormone)- usually elevated.

Urine calcium (one-day urine) – may be elevated due to hyperparathyroidism.

Some of the test results for patients with hypoparathyroidism include:

Low magnesium

High phosphate


Low calcium

Vitamin D – this test may be undertaken to establish whether an individual has a vitamin D deficiency that may be affecting calcium concentration in the blood.