Hyperparathyroidism is excessive production of parathyroid hormone 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.

There are two types of hyperparathyroidism.

Primary hyperparathyroidism is caused by enlargement of one or more of the parathyroid glands. This leads to too much parathyroid hormone, which raises the level of calcium in the blood. The term "hyperparathyroidism" generally refers to primary hyperparathyroidism.

Secondary hyperparathyroidism is when the body produces extra parathyroid hormone because the calcium levels are too low. This is seen when vitamin D levels are low or when calcium is not absorbed from the intestines. Correcting the calcium level and the underlying problem will bring the parathyroid levels in the normal range.

If the parathyroid glands continue to produce too much parathyroid hormone even though the calcium level is back to normal, the condition is called "tertiary hyperthyroidism." It occurs especially in patients with kidney problems.

Related topics:

• Parathyroid related hypercalcemia
• Primary hyperparathyroidism
• Secondary hyperparathyroidism
• Parathyroid adenoma

• Fatigue
• Back pain
• Joint pain
• Fractures of long bones
• Decreased height
• Increased urine output
• Increased thirst
• Upper abdominal pain
• Loss of appetite
• Nausea
• Muscular weakness
• Muscle pain
• Depression
• Personality changes
• Stupor and possibly coma
• Itching of the skin
• Blurred vision (because of cataracts)
• Bone pain or tenderness

Additional tests include:

• 24-hour urine collection may show increased calcium in urine.
• Bone x-ray shows bone reabsorption or fractures.
• X-rays, ultrasound, or CT scans of the kidneys or ureters may show calcification or obstruction.
• Bone density test may show reduced bone mineral density, particularly of the forearm.