Disorders of the parathyroid gland

The vital parathyroid glands (Latin: glandulae parathyroideae) comprise two lentil-sized pairs of organs or four so-called epithelial bodies (four grain-sized glands).

The parathyroid glands are independent, hormone-producing organs and, as their name suggests, are found in the immediate vicinity of the thyroid gland. Usually, humans have four parathyroid glands, a lower and an upper one on both the right and left side. As with the thyroid gland itself, they are hormone-producing glands that perform various processes, including regulating the calcium level in the blood.

Parathyroid glands are the only producers of the parathyroid hormone, which is essential for regulating the calcium balance in the human body. The parathyroid hormone controls calcium excretion via the kidneys, promotes calcium absorption in the intestine and can extract calcium from the bones if necessary. In order to carry out these processes, the parathyroid hormone requires vitamin D. Calcium is needed for the construction of teeth and bones and for the proper functioning of muscles and nerves.

Types

As with the thyroid gland itself, the parathyroid glands can also become pathologically underactive or overactive, whereby the vast majority of parathyroid disorders are caused by different forms of parathyroid gland overactivity (known medically as hyperparathyroidism).

  • Primary hyperparathyroidism (PHPT): This is where one of the parathyroid glands produces too much parathyroid hormone independently (i.e. independently of the other parathyroid glands). Usually only one of the parathyroid glands is overactive.
  • Secondary hyperparathyroidism (SHPT), also known as renal (kidney-related) or intestinal hyperparathyroidism: Here, there is an enlargement of all four parathyroid glands in connection with kidney or intestinal disease. Like PHPT, SHPT is characterised by an increased concentration of parathyroid hormone in the blood.
  • An underactive parathyroid, which results in too low a parathyroid hormone level, is referred to as hypoparathyroidism.

Symptoms

When it comes to symptoms, a distinction must first be made between overactive and underactive parathyroid glands.

The symptoms of hypoparathyroidism manifest themselves as follows:

  • severe muscle cramps all over the body or abdominal cramps
  • impaired vision
  • calcification of large parts of the brain and the heart muscle

In contrast, overactivity of the parathyroid glands leads to too much calcium entering the bloodstream, causing stones to form in the kidney and bile, weakening the bones (known as osteoporosis) and pain in the gastric mucosa, as excess calcium leads to increased acid formation in the stomach.

In the case of intestinal hyperparathyroidism, symptoms similar to those of a vitamin D deficiency also appear, such as increasing pain in the skeletal system, especially in parts of the body that are weight-bearing (such as the lower extremities, the hips or the spine). Other complications include bone pain, an increased risk of vascular diseases such as a stroke, heart attacks or diseases of the blood vessels in the legs. Fatigue and depression are also possible.

In contrast, renal hyperparathyroidism not only presents with symptoms of a surplus in the parathyroid hormone, but also with symptoms of renal insufficiency (also: kidney weakness, kidney failure – in this case, the kidneys are no longer able to excrete toxins via the urine, or this function is very limited). These symptoms include, but are not limited to:

  • bone pain,
  • susceptibility to fracture,
  • loosening of the teeth,
  • skeletal deformities (so-called humpback),
  • tendon tears,
  • muscle weakness,
  • (presumed) gout attacks and
  • joint calcification.

Causes

The development of hypoparathyroidism is usually triggered by surgery on the thyroid gland, during which the parathyroid glands were also removed. In addition, even minor impairments in the vascular supply of the parathyroid glands can lead to underactivity.

In 80% of cases, the increased parathyroid hormone secretion in overactive parathyroid glands is due to (usually benign) cell growth. Only very rarely are such tumours malignant.

If renal hyperparathyroidism is present, the increased production of parathyroid hormone is due to renal insufficiency. This is due to the fact that the vitamin D ingested via the diet is no longer sufficiently converted into its active hormonal form (calcitriol), which promotes the absorption of calcium into the bloodstream. A lack of calcitriol leads to increased parathyroid hormone levels and, conversely, to a decrease in calcium levels, which in turn stimulates the release of the parathyroid hormone.

In the case of intestinal hyperparathyroidism, on the other hand, the decreased calcium levels and the resulting increased parathyroid hormone levels are caused by the low calcium and/or vitamin D intake and/or the reduced absorption of both micronutrients by the intestinal wall.

Diagnosis

Parathyroid disease is usually quite easy to diagnose, as parathyroid hormone levels and calcium levels in the blood can now be measured by simple tests, making it possible to detect the disease at an early stage. Increased levels of the parathyroid hormone and insufficient calcium levels allow secondary HPT to be distinguished from primary HPT, in which both the parathyroid hormone and the calcium concentration in the blood are increased.

An ultrasound examination (sonography) can help to detect any enlarged parathyroid glands. The endocrinologist can also have the level of calcium excretion in the urine checked.

In addition, the doctor will refer the patient for an X-ray examination and/or further lab tests that may support the diagnosis of parathyroid disease. The values measured in these laboratory tests include the parameters of renal function (i.e. creatinine and urea), phosphate levels, levels of alkaline phosphatase (an enzyme) and the level of the vitamin D hormone known as calcitriol.

In the case of primary hyperparathyroidism, a nuclear medicine function test of the parathyroid glands (scintigraphy) may also be useful.

Treatment

If there is a significant pathological shift in blood calcium levels due to parathyroid disease, medical intervention is usually also required.

If the parathyroid gland is not functioning properly, a hormone injection can be administered to compensate for the lack of production. However, the parathyroid hormone cannot be replaced functionally, which means that only the effects can be treated. In the future, the patient will therefore have to take vitamin D and calcium for life.

In the case of an overactive parathyroid gland, surgery is usually performed.

The operation (called a ‘parathyroidectomy’ or PTX) is performed under general anaesthetic using a cosmetically favourable incision (minimally invasive) in a skin fold. Primary hyperparathyroidism is treated by complete removal of the diseased parathyroid gland (total parathyroidectomy). In renal hyperparathyroidism, however, three parathyroid glands are completely removed and a small remainder of the fourth parathyroid gland is preserved (subtotal parathyroidectomy).

The parathyroid glands are removed using magnifying glasses and a device that continuously monitors the function of the vocal cord nerve during surgery (neuromonitoring). This is extremely important in order to avoid injury to the vocal cord nerve and the healthy parathyroid glands.

The procedure is usually performed with minimally invasive endoscopic assistance. This means that the cut can be reduced to a maximum of 2 cm and is hardly visible after a few months. After resection of a parathyroid adenoma, normalisation of PTH/calcium metabolism is monitored by intraoperative blood testing, the results of which are reported to the operating team in theatre. Simply put, surgery is deemed successful if the parathyroid hormone level drops by more than 50% after resection.

Aftercare

Immediately after surgery, most patients develop a mild to moderate sore throat, similar to a throat infection. The symptoms are treated with painkillers and usually settle over the next two days. On the first day of the operation, blood tests are taken and the function of the vocal cord nerve is checked by an ear, nose and throat specialist.

The concentration of parathyroid hormone normalises during surgery, which in some patients manifests itself as tingling in the fingertips or a feeling of numbness around the mouth. After surgical removal of the proliferating parathyroid gland (parathyroidectomy), the symptoms subside. Patients often feel much fitter and experience reduced fatigue. Following surgery, patients often describe the sensation as having had a heavy weight lifted off their shoulders . The normalisation of calcium metabolism prevents chronic damage to the kidneys, blood vessels and bones.

Postoperatively, it is recommended that in future patients ensure that they include enough calcium in their diet. By consuming plenty of milk and dairy products, the recommended amount of calcium of about 1000 mg per day can be reached. In addition, the doctor may recommend administering the vitamin D hormone (calcitriol) as a treatment for parathyroid disease.

FAQs

What long-term effects are to be expected following a parathyroidectomy?

It is generally not necessary to take medication permanently after a PTX. Injuries to the vocal cord nerve are rare (about two to three percent) and then almost always of a temporary nature (such injuries manifest themselves as hoarseness).

What is the function of calcium in the body?

Calcium influences various metabolic processes and bodily functions and is essentially the most important building block for human bones and teeth. Calcium also affects, for example, the function of the muscles, the heart or blood clotting.

How can an overactive parathyroid gland be diagnosed?

An overactive parathyroid glands usually begins gradually and without the typical early signs. As a rule, the malfunction is noticed by a pathological blood calcium level as part of a routine laboratory check-up by your doctor.

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