The Parathyroid Glands

The parathyroid glands are small glands in the neck that produce parathyroid hormone (PTH).
The parathyroid glands are about the size of a grain of rice. There are usually four parathyroid glands, but some individuals may have six, eight, or even more parathyroid glands. They are usually located on the rear surface of the thyroid gland, one above the other on each side of the thyroid, or, in rare cases, within the thyroid gland itself or in the chest. Parathyroid glands control the amount of calcium in the blood and within the bones.

The parathyroid glands are named for their proximity to the thyroid but serve a completely different role than the thyroid gland. The parathyroid glands are quite easily recognizable from the thyroid as they have densely packed cells, in contrast to the follicle structure of the thyroid. During surgery, however, they are harder to differentiate from the thyroid or fat.
In the histological sense, they distinguish themselves from the thyroid gland, as they contain two types of cells: parathyroid chief cells and oxyphil cells.

The major function of the parathyroid glands is to maintain the body’s calcium level within a very narrow range, so that the nervous and muscular systems can function properly. When blood calcium levels drop below a certain point, calcium-sensing receptors in the parathyroid gland are activated to release hormone into the blood. PTH is a small protein that takes part in the control of calcium and phosphate homeostasis, as well as bone physiology. Parathyroid hormone has effects antagonistic to those of calcitonin. PTH increases blood calcium levels by stimulating osteoclasts to break down bone and release calcium. PTH also increases gastrointestinal calcium absorption by activating vitamin D, and promotes calcium conservation (reabsorption) by the kidneys. PTH affects the perception of well being and absence of PTH can be associated with feeling of fatigue and anxiety.

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Hypoparathyroidism

Overview
Hypoparathyroidism is a rare condition in which your body secretes abnormally low levels of parathyroid hormone (PTH). This hormone plays a key role in regulating and maintaining a balance of your body’s levels of two minerals — calcium and phosphorus.
The low production of parathyroid hormone in hypoparathyroidism leads to low ionized calcium levels in your blood and bones and to an increased amount of phosphorus.

Causes

The most common cause of hypoparathyroidism is injury to the parathyroid glands during head and neck surgery. Rarely, hypoparathyroidism is a side effect of radioactive iodine treatment for hyperthyroidism.
Hypoparathyroidism may also be caused by

  • Low blood magnesium levels
  • Metabolic alkalosis
  • Extensive cancer radiation treatment of your face or neck, which can result in destruction of your parathyroid glands, or occasionally because of radioactive iodine treatment for hyperthyroidism.

DiGeorge syndrome is a childhood disease in which hypoparathyroidism occurs because all the parathyroid glands are missing at birth. Familial hypoparathyroidism occurs with other endocrine diseases, such as adrenal insufficiency, in a syndrome called type I polyglandular autoimmune syndrome (PGA I).
The risk factors for hypoparathyroidism include recent thyroid or neck surgery, a family history of parathyroid disorder, or certain autoimmune diseases such as Addison’s disease.

Symptoms

  • Abdominal pain
  • Brittle nails
  • Cataracts
  • Dry hair
  • Dry, scaly skin
  • Muscle aches or cramps in your legs, feet, abdomen or face
  • Muscle spasms called tetany (can affect the larynx, causing breathing difficulties)
  • Pain in the face, legs, and feet
  • Seizures
  • Weakened tooth enamel (in children)
  • Decreased consciousness
  • Delayed or absent tooth formation
  • Hand or foot spasms
  • Painful menstruation
  • Tingling or burning (paresthesias) in your fingertips, toes and lips
  • Twitching or spasms of your muscles, particularly around your mouth, but also in your hands, arms and throat
  • Fatigue or weakness
  • Patchy hair loss, such as thinning of your eyebrows
  • Anxiety or nervousness
  • Headaches
  • Depression, mood swings
  • Memory problems

Testing

Blood tests will be done to check calcium, phosphorus, magnesium, and PTH levels. An ECG may show abnormal heart rhythms.
A urine test may be done to determine how much calcium is being removed from the body.

Treatment

To restore the calcium and mineral balances in the body. Treatment involves calcium carbonate and vitamin D supplements, which usually must be taken for life. Blood levels are measured regularly to make sure that the dose is correct. A high-calcium, low-phosphorous diet is recommended.
Persons who have life-threatening attacks of low calcium levels or prolonged muscle contractions are given calcium through a vein (IV). Precautions are taken to prevent seizures or larynx spasms. The heart is monitored for abnormal rhythms until the person is stable. When the life-threatening attack has been controlled, treatment continues with medicine taken by mouth.

Expectations (prognosis)

The outcome is likely to be good if the diagnosis is made early. However, changes in the teeth, the development of cataracts, and brain calcifications are irreversible.

Complications

Hypoparathyroidism in children may lead to stunted growth, malformed teeth, and slow mental development.
Over-treatment with vitamin D and calcium can cause hypercalcemia (high blood calcium) and may sometimes interfere with kidney function.
Hypoparathyroidism increases your risk of pernicious anemia, Addison’s disease, cataracts, and Parkinson’s disease.

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Primary Hyperparathyroidism

Overview

Hyperparathyroidism is excessive production of parathyroid hormone (PTH) by the parathyroid glands. The parathyroid glands are located in the neck, near or attached to the back side of the thyroid gland. They produce parathyroid hormone, which controls calcium, phosphorus, and vitamin D levels within the blood and bone. When calcium levels are too low, the body responds by increasing production of parathyroid hormone. This increase in parathyroid hormone causes more calcium to be taken from the bone and more calcium to be reabsorbed by the intestines and kidney. When the calcium level returns to normal, parathyroid hormone production slows down. Hyperparathyroidism can be primary or secondary.

Neonatal hyperparathyroidism. Severe, untreated hyperparathyroidism in pregnant women may cause dangerously low levels of calcium in newborns.

Cause

Primary hyperparathyroidism is caused by swelling of one or more of the parathyroid glands. This leads to the release of too much parathyroid hormone, which raises the level of calcium in the blood.

    • A noncancerous growth (adenoma) on a gland is the most common cause.
    • Enlargement (hyperplasia) of two or more parathyroid glands accounts for most other cases.
    • A cancerous (malignant) tumor is a rare cause of primary hyperparathyroidism.
    • Rarely, the disease is caused by parathyroid cancer.
    • The disease is most common in people over 60, but can also be seen in younger adults.

Hyperparathyroidism in childhood is very unusual.

  • Women are more likely to be affected than men. Radiation to the head and neck increases your risk.

Symptoms

  • Decreased height
  • Depression
  • Fatigue
  • Fractures
  • Increased urination
  • Kidney stones
  • Loss of appetite
  • Muscle weakness and pain
  • Nausea
  • Personality changes
  • Upper abdominal pain
  • Stupor and possibly coma
  • Osteoporosis or osteopenia
  • Forgetfulness
  • Bone and joint pain
  • Vomiting

Testing

Blood tests will be done to check for increased levels of parathyroid hormone (PTH), calcium, and alkaline phosphatase, and lower levels of phosphorus.
Bone x-rays and a bone mineral density test can help detect bone loss, fractures, or bone softening.
X-rays, ultrasound, or CT scans of the kidneys or urinary tract may show calcium deposits or a blockage.
A sestamibi scan is a specially designed radioactive compound that is absorbed by overactive parathyroid glands and can be detected on computerized tomography (CT) scans. A small dose of the compound is injected into your bloodstream before the imaging test is done.

Treatment

Your doctor may recommend no treatment and regular monitoring if:

  • Your calcium levels are only slightly elevated
  • Your kidneys are functioning normally
  • Your bone density is normal or only slightly below normal
  • You have no other symptoms that may improve with treatment

If you choose this watch-and-wait approach, you’ll likely need a test to check your blood-calcium levels at least twice a year and have other monitoring tests done at least once a year.

Surgery

Surgery is the most common treatment for primary hyperparathyroidism and provides a cure in at least 90 percent of all cases. A surgeon will remove only those glands that are enlarged or have a tumor (adenoma). If all four glands are affected, a surgeon will likely remove only three glands and perhaps a portion of the fourth — leaving some functioning parathyroid tissue.
Surgery may be done as an outpatient procedure, allowing you to go home the same day. In such cases, the surgery is done through very small incisions in the neck, and you receive only local anesthetics.
Complications from surgery aren’t common. Risks include:

  • Damage to nerves controlling the vocal cords
  • Long-term low calcium levels requiring the use of calcium and vitamin D supplements

Drugs

Medications to treat hyperparathyroidism include the following:

  • Calcimimetics. A calcimimetic is a drug that mimics calcium circulating in the blood. Therefore, the drug may trick the parathyroid glands into releasing less parathyroid hormone. This drug is sold as cinacalcet (Sensipar). The Food and Drug Administration approved cinacalcet to treat hyperparathyroidism caused by chronic kidney disease or parathyroid cancer. Some doctors may prescribe it to treat primary hyperparathyroidism, particularly if surgery hasn’t successfully cured the disorder or a person isn’t a good candidate for surgery.
  • Hormone replacement therapy. For women who have gone through menopause and have signs of osteoporosis, hormone replacement therapy may help bones retain calcium.

You may be at an increased risk of primary hyperparathyroidism if you:

  • Are a woman who has gone through menopause
  • Have had prolonged, severe calcium or vitamin D deficiency
  • Have a rare, inherited disorder, such as multiple endocrine neoplasia, type I, which usually affects multiple glands
  • Have had radiation treatment for cancer that has exposed your neck to radiation
  • Have taken lithium, a drug most often used to treat bipolar disorder


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Secondary Hyperparathyroidism

Secondary hyperparathyroidism is the result of another condition that lowers calcium levels. Therefore, your parathyroid glands overwork to compensate for the loss of calcium. Factors that may contribute to secondary hyperparathyroidism include:

  • Severe calcium deficiency. Your body may not get enough calcium from your diet, often because your digestive system doesn’t absorb the calcium you consume.
  • Severe vitamin D deficiency.Vitamin D helps maintain appropriate levels of calcium in the blood, and it helps your digestive system absorb calcium from your food. Your body produces vitamin D when your skin is exposed to sunlight, and you consume some vitamin D in food. If you don’t get enough vitamin D, then calcium levels may drop.
  • Chronic kidney failure. Your kidneys convert vitamin D into a form that your body can use. If your kidneys function poorly, useable vitamin D may decline and calcium levels drop. Chronic kidney failure is the most common cause of secondary hyperparathyroidism.

Neonatal hyperparathyroidism. Severe, untreated hyperparathyroidism in pregnant women may cause dangerously low levels of calcium in newborns.

Symptoms

  • Decreased height
  • Depression
  • Fatigue
  • Fractures
  • Increased urination
  • Kidney stones
  • Loss of appetite
  • Muscle weakness and pain
  • Nausea
  • Personality changes
  • Upper abdominal pain
  • Stupor and possibly coma
  • Osteoporosis or osteopenia
  • Forgetfulness
  • Bone and joint pain
  • Vomiting

Testing

Blood tests will be done to check for increased levels of parathyroid hormone (PTH), calcium, and alkaline phosphatase, and lower levels of phosphorus.
Bone x-rays and a bone mineral density test can help detect bone loss, fractures, or bone softening.
X-rays, ultrasound, or CT scans of the kidneys or urinary tract may show calcium deposits or a blockage.

Treatment

Supplementation of the deficiencies.

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