Parathyroid adenoma is a benign hormone-active tumor of the parathyroid gland, accompanied by excessive secretion of parathyroid hormone and hyperparathyroidism. With parathyroid adenoma, hypercalcemia develops, which can manifest itself as bone (osteoporosis, pathological fractures), renal (nephrolithiasis), gastrointestinal (gastric ulcer, pancreatitis), cardiovascular (arterial hypertension) clinical syndromes. Diagnosis of parathyroid adenoma includes laboratory tests (determination of the level of parathyroid hormone, Ca, phosphorus, alkaline phosphatase, daily excretion of Ca), X-ray examination (overview urography, bone radiography, densitometry), radioisotope scanning, ultrasound, MRI, CT of the parathyroid glands; selective angiography; biopsy with cytological examination of the material. The treatment consists in removing the parathyroid adenoma.
35.1 Benign neoplasm of the parathyroid gland
Parathyroid adenoma is a solitary or multiple tumor that produces excessive amounts of parathyroid hormone, which leads to an increase in serum calcium. In endocrinology, parathyroid adenoma causes primary hyperparathyroidism in 80-89% of cases. The disease is 2-3 times more often diagnosed in women; the age of patients with parathyroid adenoma varies from 20 to 50 years. The tumor can have a mass of 25 to 90 g, size – from 1.5 to 10 cm in diameter. Cancer from parathyroid adenoma develops in 2% of cases.
Causes of parathyroid adenoma
According to modern concepts, parathyroid adenoma can be caused by two types of mutations: a mutation in the mechanism of mitotic control or a mutation of final control in the process of secretion of parathyroid hormone.
One or another mutation affects one of the genes encoding proteins that are involved in the transport of calcium to parathyroid cells. As a result, mutant parathyroid cells acquire increased mitotic and secretory activity, begin to divide uncontrollably, giving rise to parathyroid adenoma, autonomously producing parathyroid hormone. Injuries and irradiation of the head and neck area predispose to the development of parathyroid adenoma.
Parathyroid glands are small endocrine formations adjacent to the posterior surface of the thyroid gland. Usually a person has two pairs of parathyroid glands (upper and lower), however, in some cases additional parathyroid formations may be detected in the thickness of the thyroid gland, mediastinum, retroesophageal space, near the vascular bundle, etc. Being glands of internal secretion, the parathyroid glands produce parathyroid hormone, which, along with calcitonin and vitamin D, participates in the regulation of calcium-phosphorus metabolism in the body.
Usually, a parathyroid adenoma is a yellowish-brown tumor node, with a soft consistency and clear contours, which often contains cysts. In most cases, parathyroid adenoma affects one of the lower pair of glands, parathyroid adenomas of two or more glands are less common, which requires differential diagnosis with diffuse hyperplasia of the parathyroid glands.
Depending on the histomorphological structure, there are:
- benign epitheliomas of the parathyroid glands;
- adenoma of the main light cells (watery cell adenoma);
- adenoma of the main dark cells;
- adenoma from acidophilic cells, adenolipoma (lipoadenoma).
Symptoms of parathyroid adenoma
Clinical manifestations of parathyroid adenoma can be variable. There are renal, bone, cardiovascular, gastrointestinal forms of hyperparathyroidism caused by parathyroid adenoma.
Typical common symptoms are malaise, loss of appetite, weight loss, nausea, vomiting, constipation, diffuse bone pain, arthralgia, muscle weakness, especially in the proximal extremities. The development may be accompanied by polydipsia and polyuria, mental changes (memory impairment, depression, seizures, comatose state).
Most patients develop a bony form of hyperparathyroidism. The lesion of the bone system is manifested by generalized fibrocystic ostitis, osteoporosis, pathological fractures of tubular bones and vertebral bodies, loosening and loss of teeth. The renal form of hyperparathyroidism associated with parathyroid adenoma may occur in the form of urolithiasis or diffuse nephrocalcinosis.
In the gastrointestinal form of primary hyperparathyroidism, ulcers of the stomach or duodenum with frequent exacerbations, cholecystitis, pancreatitis with severe pain syndrome, vomiting and steatorrhea may occur. Disorders of the cardiovascular system are usually expressed by arterial hypertension, calcification of the heart valves and coronary arteries.
Due to hypercalcemia, patients with parathyroid adenoma may have joint damage (chondrocalcinosis), deposition of calcium salts in the cornea of the eye (rim keratitis), dry and itchy skin, calcification of the auricles. Excessive deposition of calcium into the heart muscle can cause acute myocardial infarction; with necrosis of the renal tubules, a picture of acute renal failure develops.
If the level of calcium in the blood is higher than 3.5 mmol / l, a hypercalcemic crisis may develop. In this case, indomitable vomiting, epigastric pain, oliguria and anuria, confusion, cardiovascular insufficiency, severe gastrointestinal bleeding, intravascular thrombosis are noted.
Examination of patients with primary hyperparathyroidism, developed against the background of parathyroid adenoma, requires the participation of an endocrinologist, gastroenterologist, cardiologist, nephrologist, neurologist. Typical biochemical markers of parathyroid adenoma are hypercalcemia, hypophosphatemia, increased activity of alkaline phosphatase.
In 2/3 of patients, increased excretion of phosphorus, calcium, hydroxyproline in the urine is detected. The level of parathyroid hormone, osteocalcinin, markers of bone resorption in peripheral blood is examined without fail; in some cases, selective vein catheterization and determination of parathyroid hormone content in blood flowing from the gland are resorted to.
In order to clarify the nature of hyperparathyroidism and visualization of adenoma, ultrasound of the thyroid and parathyroid glands, thermography, scintigraphy, arteriography, CT, MRI are performed. A fine needle biopsy with a cytological examination of the punctate allows you to confirm the diagnosis and determine the form of parathyroid adenoma.
To assess the severity of the lesion of the bone system, radiography of the bones of the feet, hands, lower leg, skull, densitometry is performed. It is typical to detect signs of diffuse demineralization of bone tissue or fibrocystic ostitis. With a review urography, ultrasound of the kidneys and bladder, single or multiple stones are detected. The state of the digestive organs is assessed by ultrasound of the abdominal cavity (gallbladder, pancreas), EGD. With cardiovascular symptoms, ECG, EchoCG, daily monitoring of ECG and blood pressure are indicated.
The bone form of hyperparathyroidism should be distinguished from fibrous dysplasia, osteogenesis imperfecta, Paget’s disease, senile osteoporosis, myeloma, acromegaly, sarcoidosis, hyperthyroidism.
Treatment of parathyroid adenoma
Surgical treatment is indicated, however, conservative therapy aimed at combating hypercalcemia is necessary at the preoperative stage. The patient is transferred to a diet that restricts the intake of calcium-containing products. Intravenous infusions of isotonic sodium chloride solution, biphosphonates, forced diuresis are prescribed. With the development of a hypercalcemic crisis, it is necessary to administer a solution of glucose, sodium bicarbonate, cardiac glycosides of corticosteroids.
After appropriate preoperative preparation, the parathyroid adenoma is removed by an open method, mini-access or video endoscopic method. During the operation on the parathyroid glands, it is important to examine all the glands, to constantly monitor the level of calcium in the blood, cardiac activity, the condition of the recurrent nerves and the safety of the patient’s voice. With multiple adenomas or total hyperplasia of the parathyroid glands, their subtotal removal or total removal with autotransplantation of parathyroid tissue is indicated.
In the postoperative period, constant monitoring of the ECG, monitoring of the calcium content in the blood is carried out. Usually, after removal of the parathyroid adenoma, the level of calcium in the blood normalizes within 2 days. In some cases, transient hypocalcemia may develop, requiring appropriate treatment.
To restore bone tissue, vitamin D3, therapeutic gymnastics, spine and limb massage, estrogens are prescribed (for women during menopause). With severe lesions of the internal organs, the prognosis may be unfavorable.