Hypoparathyroidism

Hypoparathyroidism is a rare disorder of calcium metabolism.¹

The body has four parathyroid glands, which are pea-sized and located in the neck behind the thyroid gland.² The parathyroid glands make parathyroid hormone (PTH) and are part of the endocrine system.

PTH regulates the amount of calcium and phosphorus in the blood through its direct effects on the kidney and bone, where the body stores most of its calcium.

Decreased PTH levels lead to low calcium levels and high phosphorus levels in the blood. This imbalance can lead to problems with muscles, teeth, and nerve endings.¹

People with hypoparathyroidism have low or undetectable levels of parathyroid hormone (PTH) and low levels of calcium in the blood. Chronic symptoms may include:¹

• Tingling in the lips, fingers, and toes
• Muscle cramps and spasms (called tetany) that cause pain in the face, hands, legs, and feet
• Muscle weakness and generalized fatigue
• Problems with the teeth, including weakened enamel
• Calcium deposits in the brain or kidney
• Seizures
• Cataracts
• Increased risk of kidney problems

The most common cause of hypoparathyroidism is injury to the parathyroid glands during head and neck surgery. For example, thyroid surgery can damage the parathyroid glands or the surrounding tissues.¹

In adults, the disorder usually is a complication of neck surgery. In children, it is most often due to an inherited disorder. Congenital hypoparathyroidism, which can be present at birth or appear in early childhood, may be caused by a genetic variant or mutation. Some cases of congenital hypoparathyroidism may be part of a syndrome, meaning it is one of several symptoms, while in other instances the problem occurs by itself.¹

Autoimmune polyglandular failure type 1 (APS-1) is a rare inherited autoimmune disease including hypoparathyroidism. APS-1 is usually diagnosed in early childhood, and hypoparathyroidism is usually the first of several hormonal deficiencies to appear.^2,3

To diagnose hypoparathyroidism, a healthcare provider will usually start with a blood test to determine the levels of the following:^1,2

• Parathyroid hormone
• Calcium
• Phosphorus
• Creatinine
• Magnesium

A urine test determines how much calcium the kidneys are releasing.

Unlike most other hormonal deficits, hypoparathyroidism is not treated with replacement of the missing hormone, parathyroid hormone (PTH).

Currently, the standard treatment for hypoparathyroidism consists of activated vitamin D (calcitriol) and calcium supplements. Some people may also need magnesium supplementation. Conventional therapy requires many pills taken throughout the day.^1,2

Diet recommendations usually include eating foods high in calcium, such as dairy products, breakfast cereals, fortified orange juice, and green, leafy vegetables, or avoiding foods high in phosphorus, such as meat, poultry, fish, nuts, whole grains, and beans.^3,4

Conventional therapy with vitamin D and calcium may lead to a buildup of calcium in the kidneys. This buildup may lead to problems, including kidney stones and deposits of calcium, reduced kidney function, tissue damage, or even kidney failure.

The development of PTH as a replacement therapy in patients with hypoparathyroidism was first explored by NICHD investigators beginning in 1992. Since then, NICHD researchers have conducted a series of classic studies evaluating PTH 1-34 regimens, including once-daily and twice-daily PTH injections without concurrent use of calcitriol or calcium supplements in adults and children. Recently, these NICHD researchers introduced PTH delivery by an insulin pump in two landmark studies in adults⁵ and in children.^6,7,8,9,10 In January 2015, the U.S. Food and Drug Administration approved PTH 1-84 for adult hypoparathyroidism patients who do not respond well to standard treatment, as an add-on to that treatment.¹¹