Hyperparathyroidism is characterized by an increased concentration of parathyroid hormone in the blood. Parathyroid hormone is responsible for regulating the level of calcium in the blood serum. The condition can be completely asymptomatic or cause the most severe symptoms.
What is hyperparathyroidism?
The common feature of all forms of hyperparathyroidism is the increased concentration of parathyroid hormone in the blood. Here, parathyroid hormone functions to increase blood calcium concentrations by activating bone resorption while decreasing phosphate concentrations by increasing renal excretion. The counterpart of the parathormone is the hormone calcitriol. Both hormones are produced in the parathyroid glands. The parathyroid glands represent four small epithelial bodies, usually located at the upper and lower poles of the thyroid gland. Hyperparathyroidism is not a single disease, but a collective term for various disorders with different causes. In most cases, the disease is asymptomatic. However, a distinction is made between asymptomatic and symptomatic hyperparathyroidism. There are five different forms of this disorder, which are divided into primary, secondary, tertiary, quaternary and quintary hyperparathyroidism. The primary form of this disorder is most common. Quaternary or quintary hyperparathyroidism is very rare.
Causes
All five types of hyperparathyroidism have different causes. In primary hyperparathyroidism, there is usually a benign tumor of one or more parathyroid glands. More hormone-producing cells exist, so hormone secretion is increased. A benign tumor of the glandular tissue, in this case the parathyroid gland, is called an adenoma. The adenoma is largely disconnected from the regulatory circuit within the hormonal system. In rare cases, however, a carcinoma of the parathyroid gland can be hidden behind it. Normally, an increased calcium level in the blood causes the production of parathyroid hormone to stop via binding to receptors until the calcium level has dropped again. In primary hyperparathyroidism, however, no significant reduction in hormone production can be achieved even by slightly elevated blood calcium levels. Only when the values are more elevated does this come to a halt. However, this can lead to a considerable loss of bone substance. Missing minerals in the bones are replaced by connective tissue. Simultaneous hemorrhages into the bone substance result in so-called brown tumors from fusing bone cysts. In secondary hyperparathyroidism, increased production of parathyroid hormone is provoked by chronically low blood calcium levels. By increasing the production of parathyroid hormone, the body attempts to compensate for the calcium level. However, it fails to do so, resulting in permanent hyperparathyroidism. Causes of low calcium levels can be vitamin D deficiency, malabsorption of calcium in the intestine, or renal insufficiency. In renal dysfunction, phosphates are insufficiently excreted in the urine. These then bind calcium and thereby lower the calcium level in the blood. Secondary hyperparathyroidism based on renal insufficiency may progress to tertiary hyperparathyroidism. The tertiary form of the disease is again similar to primary hyperparathyroidism. Chronic renal failure requires sustained increased production of parathyroid hormone to raise blood calcium levels. This stimulates the growth of the adrenal glands. As in the case of adenoma, the glandular tissue is enlarged here, again disconnecting hormone production from the regulatory circuit. When renal damage develops due to the effect of primary hyperparathyroidism, the secondary overproduction of parathyroid hormone caused on this basis is called quaternary hyperparathyroidism. After quaternary hyperparathyroidism has persisted for some time, decoupling also occurs, and quintary hyperparathyroidism develops.
Symptoms, complaints, and signs
In most cases, hyperparathyroidism is discovered only incidentally during blood tests because the condition is asymptomatic in more than 80 percent of cases.Occasionally, however, those affected complain of nonspecific complaints such as fatigue, loss of appetite, mild depressive moods or mild memory impairment. Hyperparathyroidism often remains asymptomatic throughout life. However, in more severe forms of the disease, increased bone loss occurs, leading to increased bone fragility. Other symptoms include nausea, constipation, increased thirst, increased urine production, or severe loss of appetite. Calcium salts may precipitate in the kidneys with the formation of kidney stones. In the long term, this leads to renal insufficiency and even complete failure of the kidneys. Calcium can also be deposited in the arterial blood vessels, which can lead to arterial thrombosis and cardiovascular disease. Particularly in secondary hyperparathyroidism, the development of severe circulatory disorders with extensive necrosis of the skin is possible, as here unexcreted phosphates form insoluble salts with calcium that can precipitate in the arterioles.
Diagnosis and course of the disease
Accurate diagnosis of the presenting form of hyperparathyroidism is necessary for proper treatment.
Complications
Hyperparathyroidism does not necessarily cause symptoms or lead to complications in every case. Unfortunately, because the symptoms are not directly clear in most cases, this disease is recognized relatively late, so that no early treatment of hyperparathyroidism is possible. The affected person suffers from a loss of appetite, which usually leads to underweight. Furthermore, depression and other moods or memory disorders also occur. Those affected not infrequently feel tired and weary, and the fatigue cannot be compensated for by sufficient sleep. Bone loss and vomiting and nausea occur. The patient’s everyday life is very much restricted and negatively influenced by the disease. In the worst case, complete kidney failure occurs. In this case, the affected person is dependent on dialysis until a new donor kidney cannot be found. Necrosis and circulatory disorders also occur in the patient. As a rule, hyperparathyroidism can be controlled relatively well with the help of proper nutrition. This does not result in further complications. Without treatment, life expectancy may be limited by hyperparathyroidism.
Treatment and therapy
In asymptomatic hyperparathyroidism, no therapy is often necessary except for its constant monitoring. Otherwise, primary hyperparathyroidism can be completely cured by surgical removal of the adenoma. Nonsurgical therapies consist of administration of biphosphonates, calcimimetics to inhibit the excretion of parathyroid hormone, and diets low in calcium and rich in vitamin D. In secondary and quaternary hyperparathyroidism, treatment of the underlying disease predominates. If this can be cured, the overproduction of parathyroid hormone also disappears. Tertiary hyperparathyroidism is initially treated with medication. If the parathyroid hormone level still does not decrease, partial removal of the epithelial corpuscles is required.
Outlook and prognosis
The prognosis of hyperparathyroidism depends on the form of the disease. For example, primary hyperparathyroidism usually has a very good prognosis if treated. Symptoms disappear when the source of increased hormone production is removed. Primary hyperparathyroidism is the most common form of parathyroid hyperfunction. It is usually caused by a benign adenoma in the parathyroid gland. Since this adenoma produces an increased amount of parathyroid hormone, it should be surgically removed. However, without surgery, a cure for the hormone disorder is not possible. There are no drugs that could stop or limit the production of parathyroid hormone. However, there is another form of primary hyperparathyroidism, which is genetic and therefore not curable. In this case, however, only a mild hyperfunction is present. Surgery is also required for tertiary and quintary hyperparathyroidism. Since secondary hyperparathyroidism is triggered by an underlying disease, it can also only be successfully treated by therapy of this disease. Thus, along with the underlying disease, the hormonal disorder also disappears. The same applies to the treatment of quaternary hyperparathyroidism.The prognosis of these forms of hyperparathyroidism depends on the therapeutic success of the underlying disease. If hyperparathyroidism persists for a long time, kidney stones often develop. In addition, calcification of muscles and blood vessels may occur, resulting in further disease.
Prevention
No preventive measures are known for primary hyperparathyroidism. Other forms of hyperparathyroidism may be caused by renal disease. Therefore, the risk can be reduced by following general recommendations for a healthy lifestyle.
Follow-up
Following surgical treatment of hyperparathyroidism, patients often remain under medical supervision for a few days. This allows direct monitoring of calcium levels. Only when the mineral balance is in equilibrium are patients allowed to go home. Doctors recommend regular follow-up. Patients should adhere to this to ensure correct adjustment. Blood value checks can determine whether the remaining parathyroid tissue may be prone to hyperfunction again. Follow-up care should show in a timely manner if there may be a deficiency of hormones. If the disease has not been treated by surgery, a high fluid intake is important. This takes place not only during therapy, but also in the post-treatment phase. In women who have gone through menopause, biophosphonates are also used. These prevent higher bone fragility. Other active ingredients such as cinacalcet are used to alleviate the symptoms. In any case, those affected should keep regular doctor’s appointments so that any changes can be detected immediately. A change in lifestyle is generally not necessary, only a certain amount of rest may be advisable. A severe course of the disease may lead to kidney failure, in which case rapid action is required. That is why patients should know how to interpret their own body signals.
