Hyperparathyroidism is a term used to describe increased activity in one or more of the parathyroid glands. The parathyroid glands are small glands located behind the thyroid gland which produce parathyroid hormone (PTH), a hormone which controls the level of calcium in the bloodstream. Increases in the levels of PTH circulating can have a number of consequences, such as osteoporosis and kidney failure. Hyperparathyroidism can be subdivided into primary, secondary and tertiary hyperparathyroidism. Each of these conditions has a different underlying cause and different treatment options.
Primary Hyperparathyroidism
Causes
Primary hyperparathyroidism is caused by an over-production of PTH by the parathyroid glands. PTH causes the levels of calcium in the blood to rise due to increased breakdown of bone, increased absorption of calcium in the gut and decreased amounts of calcium excreted by the kidneys. Primary hyperparathyroidism is due to a problem with the parathyroid gland itself. The most common cause of primary hyperparathyroidism is due to a benign tumour of one or more of the parathyroid glands, known as parathyroid adenoma. In the majority of cases, only one parathyroid gland is affected by an adenoma, however, it is possible for multiple parathyroid glands to be affected. Very rarely, primary hyperparathyroidism may be caused by a malignant tumour of one or more parathyroid glands; known as parathyroid carcinoma. This is by far the least common cause of primary hyperparathyroidism. Another possible cause of primary hyperparathyroidism is parathyroid hyperplasia, where the parathyroid glands become enlarged. This is less common than parathyroid adenoma, but is much more common than parathyroid carcinoma. Parathyroid hyperplasia may be a genetic condition that occurs in people with a family history, but may also occur spontaneously in people with no family history.
Presentation
Primary hyperparathyroidism presents with a number of signs and symptoms. One common presenting complaint is bone and joint pain. This is due to the excessive PTH causing persistent release of calcium from the bones, weakening the bones over time and increasing their risk of fracture. There are also a number of manifestations in the urinary system. Kidney stones may develop as a result of the kidneys trying to excrete more calcium in the urine, due to the high levels in the bloodstream. Patients may feel the need to urinate more frequently, feel thirsty, lose their appetite and feel nausea or constipation. The high levels of calcium may also cause gout to occur in some patients. If left untreated for a long period of time, the high levels of calcium passing through the kidneys may lead to kidney failure.
Treatment
Treatment for primary hyperparathyroidism depends on the severity of the condition. For those patients who have only mildly elevated calcium levels and no symptoms, surgical management is not indicated. Such patients need to be vigilant with their diet. It is recommended that calcium intake is moderate, as a low intake will stimulate PTH release and that higher intakes of calcium will only add to the existing problem of high blood calcium levels. Vitamin D intake also needs to be moderate, as low levels of vitamin D can also trigger release of PTH. Other measures include keeping well hydrated to reduce the risk of kidney stones, weight-bearing physical activity to reduce bone loss, and avoiding medications and activities which may increase blood calcium levels.
Patients with symptomatic primary hyperparathyroidism and moderate to high levels of blood calcium often require surgical intervention. It is indicated in people who have reduced bone density and renal function. The problematic parathyroid gland (or glands, in some cases) is removed by a surgeon, either using a traditional approach, or minimally invasive surgery where possible. Minimally invasive surgery is assisted by imaging technology and may be performed with a nerve block, rather than under general anaesthetic. In some cases, additional surgery may be required if some abnormal parathyroid tissue remains. Sometimes, the abnormal parathyroid tissue is found in an unusual location, such as in the thoracic cavity. Surgical management produces good outcomes in the majority of cases and can relieve many of the symptoms.
Secondary Hyperparathyroidism
Causes
Secondary hyperparathyroidism is an increase in secretion of PTH in response to low levels of calcium in the blood (hypocalcaemia). In secondary hyperparathyroidism, the parathyroid glands often become enlarged. Blood calcium levels can be abnormally low for a number of reasons. Severe dietary calcium deficiency or malabsorption of calcium from the digestive system can both lead to secondary hyperparathyroidism by reducing serum calcium levels. As vitamin D is critical for the absorption of calcium in the digestive system, severe vitamin D deficiency may also produce secondary hyperparathyroidism. Vitamin D is primarily obtained from the sunlight in humans, but needs to be converted in the body to its active form, a process which involves the liver and the kidneys. Hence, kidney failure may also result in secondary hyperparathyroidism, as there is less active vitamin D production and a resultant decrease in blood calcium levels due to impaired absorption in the gastrointestinal tract.
Presentation
As with primary hyperparathyroidism, patients with secondary hyperparathyroidism are at an increased risk of fracture due to decreased bone density. Limb deformities may be present in some sufferers. The majority of patients who have chronic renal failure will have a degree of secondary hyperparathyroidism, and thus their presenting symptoms are often related to their renal failure, such as changes in urinary habits, ankle and leg oedema, nausea, vomiting and fatigue. In secondary hyperparathyroidism, calcium levels are not elevated and thus, some of the symptoms observed in patients with primary hyperparathyroidism related to excessive calcium are not observed in secondary hyperparathyroidism.
Treatment
Generally, the aim of treatment of secondary hyperparathyroidism is aimed at correcting the underlying cause of the problem. For those cases which are the result of vitamin D deficiency, supplements and a safe increase in sun exposure can help to correct the problem. Patients with chronic renal failure need to have their underlying condition treated. Some potential treatment strategies for renal failure include dialysis, control of blood pressure, kidney transplantation, phosphate binding medication and dietary restrictions. In severe cases which do not respond to other forms of treatment, sometimes surgical parathyroid removal is performed. However, there is a risk that the problem will persist or recur following surgery.
Tertiary Hyperparathyroidism
Cause
Tertiary hyperparathyroidism occurs following longstanding secondary hyperparathyroidism. Even when the underlying cause of the original low blood calcium is corrected, one or more of the parathyroid glands continues to produce increased amounts of PTH, resulting in elevated blood levels of calcium. It is common in patients who develop secondary hyperparathyroidism as a result of chronic renal failure.
Presentation
Tertiary hyperparathyroidism presents in a similar manner to primary hyperparathyroidism as both conditions manifest with elevated levels of calcium in the blood. Common symptoms of tertiary hyperparathyroidism are kidney stones, poor renal function, decreased bone density and increased fracture risk.
Treatment
Surgical management is recommended in patients with tertiary hyperparathyroidism. As with secondary hyperparathyroidism, often all four glands are involved. Affected parathyroid glands are removed by the surgeon. Patients with secondary and tertiary hyperparathyroidism are likely to have more than four parathyroid glands, and if additional glands are present, these are also removed.
If you have questions about the parathyroid glands, contact your local doctor who will arrange for you to see a thyroid surgeon.
