By Johanna Pallotta, MD and Antonia Stephen, MD
Among the many hormone disorders that fall within the category of endocrine disease, one of the most uncommon is hypoparathyroidism, a rare and complex condition in which the body secretes abnormally low levels or no parathyroid hormone (PTH). And although they have similar names and are situated close to one another, the function of the thyroid and parathyroid (parathyroid means “near the thyroid”) glands are completely separate.
What are the parathyroid glands?
The parathyroid glands are located in the mid-lower neck, usually adjacent to the thyroid gland. In their normal state, the parathyroid glands are quite small, measuring only a few millimeters in diameter and weighing, on average, less than 50 millagrams (around one–thousandth of an ounce). There are typically four parathyroid glands: two on the left and two on the right. Their function is to produce PTH, which is responsible for controlling calcium metabolism in our bodies. PTH works to keep our blood calcium level within a normal range by means of its effect on the bones, which store calcium, the intestines, which absorb calcium, and the kidneys, which excrete calcium.
When parathyroid glands are normal in size and are functioning properly, the PTH level increases slightly when the blood calcium level goes down and decreases slightly when the blood calcium level goes up. When the parathyroid glands and calcium metabolism are working normally, our bones are encouraged to absorb and deposit calcium, keeping them strong and resistant to fractures.
Hypoparathyroidism occurs when the parathyroid gland(s) do not produce adequate levels of PTH, resulting in hypocalcemia (low calcium levels), which can be harmful and life-threatening, especially when severe in the first few days following its appearance.
Having the right amount of calcium in your blood is essential to proper functioning of many organs and systems including the heart, kidneys, nervous system, bones and teeth. Thus, people who lack adequate PTH may experience muscle problems, bone damage, kidney damage, heart problems, cognitive issues and emotional swings.
What are the causes of hypoparathyroidism?
By far, the most common cause of hypoparathyroidism in adults is surgery on or around the thyroid and parathyroid glands. When the thyroid is surgically removed, the tiny parathyroid glands can be mistakenly removed or damaged, resulting in hypoparathyroidism.
Another surgical cause of hypoparathyroidism is deliberate removal of the parathyroid glands themselves. This can be necessary when the parathyroid gland(s) becomes too overactive and increase in size and PTH production (hyperparathyroidism). High levels of PTH can cause hypercalcemia (high calcium levels) and osteoporosis as well as other problems. Hyperparathyroidism usually affects one parathyroid gland, but may affect all four.
Dysfunction of the parathyroid glands after thyroid or parathyroid surgery can be temporary or permanent. Temporary hypoparathyroidism happens quite often after thyroid surgery, but the condition usually subsides within days or weeks. Fortunately, permanent hypoparathyroidism is a rare surgical complication resulting from the removal or damage of too much parathyroid tissue. Fortunately, only one parathyroid gland, or even just part of one, needs to survive and recover for the patient to have normal calcium metabolism. Permanent hypoparathyroidism happens in about 1 or 2 percent (one to two out of 100) of thyroid and parathyroid surgeries when done by a highly experienced thyroid and parathyroid surgeon.
Another cause of hypoparathyroidism is destruction of the parathyroid glands by the immune system in people with autoimmune diseases, where the body mistakenly attacks its own tissues. This condition is usually diagnosed in childhood or adolescence. Antibodies damage the parathyroid glands, and they are not able to produce enough PTH to maintain normal calcium levels.
There are other rare causes of hypoparathyroidism, including genetic disorders resulting in abnormal parathyroid gland development or PTH production; infiltration of the parathyroid glands by iron overload (hemochromatosis), an accumulation of iron in the body from any cause; granulomatous diseases (which occur when the immune system attempts to wall off substances it perceives as foreign); radiation-induced damage; or viral infections. These are all extremely rare.
What are the symptoms of hypoparathyroidism?
The symptoms of hypoparathyroidism can be acute or long-term. Those caused by an acute drop in calcium levels are related to the fact that calcium stabilizes nerves and muscles. When the calcium level in the blood is low, the nerve and muscle endings in the body become irritable. This is called “tetany.” The symptoms of tetany can be mild (numbness around the mouth, tingling in the hands and feet, muscle cramps) or severe (hand, foot and throat spasms, and seizures). The more severe symptoms of low calcium levels, if left untreated, can be life-threatening.
When the hypoparathyroidism continues for a long period of time, other organs can be affected. Some of these problems are a result of the high doses of calcium supplements needed to maintain a safe and normal blood calcium level. Kidney stones can develop if the calcium level in urine is too high. Patients with chronic hypoparathyroidism can have other effects such as basal ganglia (brain) calcifications, cataracts, skeletal changes, dental abnormalities and skin and nail changes. These problems can be minimized or avoided if the calcium level is watched carefully and remains in the recommended range.
How is hypoparathyroidism diagnosed and treated?
The diagnosis of hypoparathyroidism is made based on blood work when an abnormally low calcium level is detected with a low PTH level – usually well below the normal range in this situation. Other laboratory abnormalities include a higher-than-normal phosphate level.
Once hypoparathyroidism is diagnosed, other tests should be done to help manage and treat the patient. These tests include a blood level for vitamin D and magnesium and a collection of urine for 24 hours to measure the urine calcium level. Vitamin D and magnesium stores in the body play an important role in calcium balance, and this becomes even more important in patients with hypoparathyroidism.
At present there is no known cure for hypoparathyroidism. Treatment includes oral calcium and vitamin D. For adults with stable chronic hypoparathyroidism, the dose of oral calcium is typically one to two grams of elemental calcium daily in divided doses. This can be calcium carbonate or calcium citrate. Calcium carbonate is less expensive and works very well for most patients. Calcium citrate may be better absorbed and cause less stomach discomfort, so this may be preferred by some patients. All of these types of calcium are available as over-the-counter supplements.
The vitamin D recommended is called calcitriol or Rocaltrol® and usually requires a prescription. This special form of vitamin D should be used, since regular vitamin D supplements do not work well in patients with primary hypoparathyroidism.
An important aspect of calcium and vitamin D supplementation is that the blood calcium level should be kept in the low-normal range. The magnesium should be kept normal for PTH to be secreted and also for its actions. That is, the patient should take only enough calcium and vitamin D to keep the symptoms of hypocalcemia (low blood calcium level) at a minimum. Without enough parathyroid hormone, too much calcium may be deposited in the kidney and urine, which can lead to kidney stones and kidney damage. Keeping the blood calcium in the low-normal range prevents this. If the calcium level is allowed to get too high, or even in the mid-normal range, calcium supplementation has to be reduced.
If the calcium level cannot be maintained with calcium and vitamin D supplements and the patient is still symptomatic, another option is the addition of a special medication called recombinant PTH 1-84. This is a medication injected under the skin that should only be used with the supervision of an expert in the treatment of hypoparathyroidism. If the patient feels well on calcium and vitamin D, then this medication is not recommended.
Every patient with primary hypoparathyroidism should have an endocrinologist experienced in treating this condition and should visit with them at least every six months.
Dr. Johanna A. Pallotta, FACE, is Associate Professor of Medicine at Harvard Medical School and a Senior Physician in the Department of Medicine Division of Endocrinology and Metabolism with Beth Israel Deaconess Medical Center in Boston. Her areas of clinical interest include thyroid disease, pituitary disorders, osteoporosis and a particular expertise in parathyroid disease. In addition to caring for patients with disorders of the thyroid, pituitary and bone, she established and supervises a referral center for parathyroid problems.
Dr. Antonia Stephen received her medical degree from Harvard Medical School and completed her general surgical residency at the Massachusetts General Hospital and an endocrine surgical fellowship at the Cleveland Clinic. She then joined the surgical staff at Massachusetts General Hospital in the Division of Surgical Oncology. Her clinical practice is focused on the surgical management of patients with endocrine tumors. Her particular areas of clinical expertise are in minimallyinvasive parathyroid surgery, the treatment of thyroid cancer and laparoscopic adrenal surgery. She also performs in-office ultrasound and ultrasound-guided biopsies of thyroid nodules and parathyroid tumors