- The role of the parathyroid glands
- Primary hyperparathyroidism
- Secondary hyperparathyroidism
- Parathyroid cyst
The role of the parathyroid glands
What are the parathyroid glands?
The parathyroid glands are tiny organs located behind the thyroid gland. Each parathyroid gland is the size of a grain of rice. Although they are called parathyroid glands, they are separate organs from the thyroid. Parathyroid glands are derived from epithelial tissue. Normally, people have a total of four parathyroid glands. They situated on the upper and lower portions on the back of the thyroid’s left and right sides. However, there is individual variation in number and position. Some people have five or more parathyroid glands, while others only have three. Since parathyroid glands are normally quite small, they are difficult to detect with ultrasonography of the neck region.
Function of the parathyroid glands
The parathyroid glands secrete parathyroid hormone. The main function of parathyroid hormone is to regulate calcium levels in the blood. Calcium is not only the primary material in bone, but it is also an essential component for blood clotting and muscle contraction throughout the body, including the heart. Furthermore, calcium is a mineral that is required for the proper functioning of brain cells. Calcium is stored in bone. Parathyroid hormone works in combination with vitamin D to increase levels of calcium in the blood by releasing it from bone as well as absorbing it in the intestines and kidneys. The body normally regulates calcium levels in the blood to be within the range of 8.8-10.1mg/dl (values may slightly vary according to testing facilities). Calcium also functions to regulate the secretion of parathyroid hormone. If blood calcium levels decrease, then the secretion of parathyroid hormone will increase to elevate blood calcium levels. On the other hand, if blood calcium levels are too high, the secretion of parathyroid hormone will decrease, working to lower the amount of calcium in the blood. In this fashion, blood calcium levels are maintained within a fixed range.
Primary hyperparathyroidism
What is primary hyperparathyroidism?
Primary hyperparathyroidism occurs when the parathyroids pathologically secrete too much parathyroid hormone, thereby raising blood calcium levels. This can result in a variety of conditions, including kidney stones, osteoporosis, and symptoms caused by hypercalcemia. Primary hyperparathyroidism is detected in approximately 1 in 4,000-5,000 people. Most cases are benign. Since the rate of cancer in primary hyperparathyroidism is approximately 1-5%, it is rarely encountered. Hyperparathyroidism may occur due to causes other than the parathyroid glands, such as renal failure. When hyperparathyroidism is caused by the parathyroid glands themselves, it is termed “primary” hyperparathyroidism. If there is a different cause, it is called “secondary” hyperparathyroidism.
Symptoms
Three typical symptoms are as follows: (1) Bone lesions Bones become brittle and fracture easily. In severe cases, body height decreases. (2) Urolithiasis (kidney stones) (3) Hypercalcemia Associated symptoms include headache, excessive thirst, heartburn, nausea, low appetite, constipation and other digestive problems, irritability, fatigue, muscle weakness, etc. In recent years, opportunities to detect hyperparathyroidism in individuals not displaying the typical symptoms have increased. It is generally noticed when regular medical checkups and testing reveal hypercalcemia. In primary hyperparathyroidism, most individuals who have slightly elevated blood calcium levels for a short period of time display no symptoms. However, when calcium levels are high, the symptoms listed above increase in severity. In cases of parathyroid cancer, extremely high calcium levels are common, and patients easily develop the three aforementioned symptoms.Testing and examinations
(1)Diagnostic tests: blood test, urine analysis These tests diagnose primary hyperparathyroidism by measuring the blood serum calcium level, parathyroid hormone level, and calcium concentration in urine, and other factors. (2) Examinations to determine location of parathyroid tumors: Examinations include ultrasonography (echography), isotope examination (parathyroid scintigraphy: methoxy-isobutyl-isonitrile [MIBI] scintigraphy), and computed tomography (CT) examination of the neck region. Parathyroid cancer is difficult to diagnose before treatment. Therefore, a diagnosis must be made comprehensively based on symptoms, the aforementioned tests and examinations, and a histopathological examination after surgery.Treatment
If blood calcium levels exceed 11mg/dl, then we recommend surgical treatment. The primary method is to surgically remove the swollen parathyroid lesion. Patients are admitted to the hospital and undergo surgery in a state of general anesthesia. Regular monitoring and observation may be pursued in cases where there is only a mild elevation in blood calcium levels and no symptoms.Disease |
Surgical method (technique) |
---|---|
Adenoma | Removal of enlarged parathyroid glands |
Hyperplasia | After complete removal of the parathyroid glands, autotransplantation (into the forearm) of a portion of the removed parathyroid tissue |
Cancer | Removal of parathyroid as well as a portion of the thyroid gland and lymph nodes |
Daily life
For people diagnosed with hyperparathyroidism, it is important to take precautions to avoid dehydration. To prevent a rise in blood calcium levels, please diligently drink fluids and avoid consuming too much calcium. Patients with extremely high blood calcium levels and severe symptoms need to be hospitalized without delay. However, there is no need to rush to receive treatment for patients with slightly elevated blood calcium levels and no clear symptoms. They can continue to lead a normal life until a date of hospital admission is determined.
Secondary hyperparathyroidism
What is secondary hyperparathyroidism?
The cause of secondary hyperparathyroidism is not a problem in the parathyroid glands. Rather, it occurs when diseases of other parts of the body cause the parathyroids to secrete excessive levels of parathyroid hormone, leading to a loss of calcium in bones. Examples of these diseases include rickets, vitamin D deficiency, and chronic renal failure.
Typical cause: renal hyperparathyroidism A typical cause of secondary hyperparathyroidism lies with renal hyperparathyroidism. People with chronic renal failure lose the abilities to excrete phosphorus and activate vitamin D3 in their kidneys. Also, a reduction in active vitamin D3 levels decreases calcium absorption in the intestine. In other words, people with chronic renal failure have decreased calcium and increased phosphorus levels in the blood. These conditions stimulate the parathyroids and encourage the secretion of parathyroid hormone. If the parathyroids are continually stimulated for long periods, they will swell and eventually secrete excessive amounts of parathyroid hormone, regardless of blood calcium levels.
Symptoms
Excessive secretion of parathyroid hormone leads the bones to release calcium into the blood stream. This results in brittle bones and the condition of “fibrous osteitis,” causing bone pain, skeletal deformities, and pathological fractures. In addition, an excessive level of parathyroid hormone causes calcium deposition at various sites in the body (ectopic calcification), resulting in diseases such as arteriosclerosis, valvular heart disease, and arthritis.Examinations and treatment
For examinations, regular measurements are taken of the levels of calcium, phosphorus, and parathyroid hormone in the blood. Treatments to avoid renal hyperparathyroidism include following a medically designed diet and oral administration of phosphate binders. Calcium tablets and oral or intravenous administration of active vitamin D3 are also important as preventive measures if calcium levels in the blood decrease. If the disease progresses to a certain extent, internal medicine treatment is the first option. Medications given include cinacalcet (Regpara®), etelcalcetide (Parsabiv®), and evocalcet (Orkedia®). If internal medicine treatment is not effective at halting disease progression or side effects make continuing therapy difficult, surgery will be considered. For surgical treatment, the standard practice is to remove all parathyroid glands, and then transplant a portion of the resected parathyroid tissue into the forearm. ※ Regarding surgery for patients who undergo dialysis treatment, we will introduce you to another facility that is equipped for dialysis.Parathyroid cyst
What is a parathyroid cyst?
A parathyroid cyst is a condition in which a fluid filled sac develops in a parathyroid gland. For this disease, there are “nonfunctional parathyroid cysts” that do not result in increased levels of parathyroid hormone and “functional parathyroid cysts” which cause excessive secretion of parathyroid hormone. Nonfunctional parathyroid cysts In human embryos, the pharyngeal pouches (which correspond to gills in fish) descend to a location at the rear of the thyroid gland. There they form the parathyroid glands. Nonfunctional parathyroid cysts are thought to develop from tubes that are left from the descent. Functional parathyroid cysts The origin of functional parathyroid cysts is thought to be the cystic degeneration of parathyroid adenoma.
Symptoms
Nonfunctional parathyroid cysts There tends to be no symptoms observed. Functional parathyroid cysts Patients exhibit symptoms according to the degree of primary hyperparathyroidism.
Examinations and treatment
Blood tests for calcium and parathyroid hormone levels are performed to assess whether the parathyroid cysts are functional or nonfunctional. The location of cysts is determined by techniques such as ultrasonography (echography), computed tomography (CT), and isotope examination (methoxy-isobutyl-isonitrile [MIBI] scintigraphy).Nonfunctional parathyroid cysts Fine-needle aspiration therapy is used to drain the liquid contents of cysts.
Functional parathyroid cysts Surgery or monitoring and observation is selected after considering a variety of factors, including blood calcium levels, bone density, and history of kidney stones. Surgery is the standard form of treatment since functional parathyroid cysts may recur even after a patient shows improvement.