The parathyroid hormone, produced by the parathyroid glands, has the role of keeping the calcium concentration in the blood within normal limits. In particular, it deals with restoring the correct calcium levels when these drop excessively. To do this, the parathyroid hormone acts on specific target organs, which are kidney, bone and intestine. Maintaining the correct calcium level, that is, the correct calcium levels in the blood, is very important. In fact, both in conditions of hypercalcemia and in conditions of hypocalcemia, the alteration of the levels of calcium in the plasma has innumerable negative consequences for the organism. When the plasma levels of calcium rise too much there is a decrease in strength, atrophy of the muscles, lethargy , hypertension, behavioral changes, constipation and nausea. Vice versa, in conditions of hypocalcemia appear dizziness, hypotension, spasms and muscle cramps. In many cases, diseases of the parathyroid glands cause significant alterations of the calcemia. We will have in particular a "hypercalcemia when the parathyroid glands work too much and secrete an excess of parathyroid hormone. Conversely, when the parathyroid glands work too little, they don't produce enough parathyroid hormone and blood calcium levels drop.
In technical terms, when one or more parathyroid glands produce an excessive amount of parathyroid hormone, a condition known as hyperparathyroidism arises, which as we have seen is typically accompanied by hypercalcemia. The most frequent cause of hyperparathyroidism is the presence of an adenoma, that is, a benign tumor, which can develop in one or more parathyroid glands. Other cases may be due to diffuse parathyroid hyperplasia; the term hyperplasia indicates an enlargement of the parathyroid glands due to an increase in the number of cells that compose them. This hyperplasia causes an increased secretion of parathyroid with consequent hyperparathyroidism. Parathyroid cancer, which is a very rare malignancy, can also lead to excessive release of parathyroid hormone. Hyperparathyroidism can also occur in the context of multiple endocrine neoplasia (also called MEN, from multiple endocrine neoplasia). This hereditary syndrome determines the onset of various disorders, including hyperparathyroidism. In general, the lesions that affect The parathyroid glands directly determine a hyperparathyroidism called primitive. However, there are also so-called secondary forms of hyperparathyroidism; these, unlike the primary ones, do not depend on a problem affecting the parathyroid glands. Among the causes of secondary parathyroidism we remember the deficiency of vitamin D, the chronic renal failure and malabsorption syndrome, which may be the result, for example, of intestinal bypass surgery.
The most common symptoms of hyperaparathyroidism are due to chronic hypercalcemia. This condition causes the recurrent appearance of kidney stones, fatigue, abdominal pain, mental confusion and depression. All these manifestations often occur very gradually, but can sometimes appear. in an abrupt, sudden and dangerous way. In the latter case there is the so-called parathyroid crisis, which requires immediate treatment. In the long run, hyperparathyroidism can also cause bone decalcification. Due to the loss of calcium, bones become brittle and break very easily. Additionally, bone cysts can form. In the most severe chronic cases, the consequence of all these alterations at the bone level can lead to strong skeletal deformations, in the context of a disease called fibrous-cystic osteopathy.
Let us now move on to the diagnosis of hyperparathyroidism. As far as blood tests are concerned, the diagnosis is based on the finding of increased plasma levels of calcium and parathyroid hormone, as opposed to a decrease in phosphorus. In medical terms, therefore, the diagnosis of hyperparathyroidism is based on the finding of hypercalcemia, hypophosphorus and elevated levels of parathyroid hormone in the blood. Another useful test for diagnostic purposes is that of urine. In the presence of hyperparathyroidism, urinalysis allows in fact to highlight a high urinary excretion of calcium and phosphorus. As for the imaging techniques used for the study of the parathyroid glands, we remember ultrasound, scintigraphy and nuclear magnetic resonance. These tests allow to detect any parathyroid hyperplasia, that is, the increase in volume of one or more glands. They can therefore highlight the presence of an adenoma and are used in the pre-operative evaluation of the patient. In addition, radiographic examination and bone densitometry may highlight characteristic changes in the skeleton, severe demineralization and osteoporosis. It now remains for us to analyze the treatment of hyperthyroidism, which, as anticipated, is mainly surgical. Often, after the surgical removal of one or more parathyroid parathyroid glands, a significant improvement can be recorded. When the surgical risk for the patient is so high. to make the removal operation contraindicated, it is possible to resort to medical therapy, which is fundamentally based on the use of bisphosphonates. These drugs inhibit bone resorption and for this reason, in addition to restoring normal calcium in the case of hyperparathyroidism, they are also used for the prevention and treatment of osteoporosis. In addition to bisphosphonates, so-called calcium mimetic drugs may also be useful in some situations. These drugs act on the calcium receptors present on the parathyroid gland mimicking a condition of hypercalcemia; this leads the parathyroid glands to inhibit the secretion of parathyroid hormone, consequently lowering the calcemia. Currently, calcium mimetics are especially indicated in hyperparathyroidism caused by chronic renal failure.
Another dysfunction that can affect the parathyroid glands is hypoparathyroidism. This condition is due to insufficient synthesis and secretion of parathyroid hormone. More rarely, it is linked to a poor action of the same parathyroid hormone at the level of target tissues. Regardless of the causes, in the presence of hypoparathyroidism there is a reduction in the concentration of calcium in the blood. Hypoparathyroidism is therefore equivalent to hypocalcemia. The most frequent cause of hypoparathyroidism is the surgical removal, voluntary or accidental, of the parathyroid glands. For example, it can occur following thyroid surgery, due to a total parathyroidectomy or a vascular injury during operations in the neck region. Other recognized causes of hypoparathyroidism are autoimmune and congenital ones. The hypoparathyroidism resulting from all these conditions can be transient, when at least one parathyroid is healthy and retains its functionality, or it can be permanent in the event of resection or injury of all the parathyroid glands. As for the symptoms of hypoparathyroidism, the condition causes manifestations related to neuromuscular hyperexcitability. In particular, the neuromuscular system becomes more excitable and individuals may experience muscle spasms, tingling and tendon reflexes, especially in the upper limbs, hands In acute forms of hypoparathyroidism, tetany may arise, characterized by spastic contractions of the muscles that can take the form of convulsions.
As for the diagnosis of hypoparathyroidism, an unusually low level of calcium in the blood is recorded at the laboratory level, hence hypocalcemia. All this is accompanied by hyperphosphorus and low parathyroid hormone values. Hypoparathyroidism therapy aims to normalize calcium concentrations in the blood and provides for the constant administration of appropriate doses of calcium and vitamin D, in the form of calcifediol or calcitriol. Tetanic crises, on the other hand, require immediate intervention with administration of calcium intravenously This intervention is aimed at preventing the onset of laryngospasm or heart failure.
