What are the Parathyroid Glands and What Are Their Functions?
Parathyroid glands are located in the neck close to the thyroid gland. They secrete a hormone called parathyroid hormone, regulating the calcium metabolism in the body. There are usually 4 pieces of parathyroid glands, each weighing 30-40 grams. The parathyroid glands maintain the blood calcium levels within certain limits, ensure the normal functioning of nerves, muscles, the heart, kidneys, and bones.
What Is Hyperparathyroidism?
Over-secretion of the parathyroid hormone for any reason is called hyperparathyroidism. In general, hyperparathyroidism is referred to as primary hyperparathyroidism when it occurs as a result of excessive parathormone (PTH) secretion from one or more of these glands. It is called secondary hyperparathyroidism when it occurs due to other causes such as chronic renal failure or intestinal malabsorption.
Hyperparathyroidism generally occurs in one out of 1000 people. It is 4 times more common in women than in men. Moreover, its incidence increases with aging. Its random detection in routine blood tests has increased significantly in recent years.
The most common (85%) cause of over-secretion of the parathyroid hormone is the formation of a tumor in one of the parathyroid glands, which is called “adenoma” in medical language. Sometimes the enlargement of the parathyroid glands (hyperplasia at frequencies of 12-15%) or, very rarely,emergence of parathyroid gland cancers (1-2%) may cause excessive secretion of the parathyroid hormones.
What Are the Complaints Caused By Hyperparathyroidism?
Due to high parathormone levels and high blood calcium; these patients present with fatigue, lethargy, musculoskeletal pain, bone and back pain, excessive water intake, frequent urination during the night, constipation, depression, anorexia, nausea, itching, peptic ulcer pain, pancreatitis, kidney stones, osteoporosis, bone cyst and tumors, pathological ECG findings, heartburn, memory impairments, and drowsiness. Pathological bone fractures may occur. Occasionally, coma and cardiac arrest may occur resulting from hypercalcemic crisis. Nowadays, advances in diagnostic techniques and laboratory tests allowed physicians to identify this disorder in asymptomatic patients randomly.
How Should the Diagnosis Be Made?
Calcium and parathyroid hormone levels are quantified in the blood for diagnosis. Blood calcium levels should be evaluated together with albumin levels. When the calcium levels are found high at least twice, other tests should be performed. The first test is to measure the parathyroid hormone levels. When both the blood calcium and parathormone levels are high, hyperparathyroidism is diagnosed. Calcium excretion in the 24-hour urine should be evaluated to exclude or find out familial benign hypercalcemia.
Blood vitamin D values should also be tested. When vitamin D is low, parathormone may be over-secreted to raise its levels. Increased blood calcium and excessive secretion of parathormone reduce serum phosphate levels; serum chloride values may be normal or high, and serum alkaline phosphatase values may rarely be high due to elevated levels of urea and creatinine and due to osteoporosis.
A biochemical diagnosis of the disease is made based on the results of laboratory tests. As it is known, imaging methods are used for identifying the disordered parathyroid gland for surgery, among on the average of four parathyroid glands in the patient.
Parathyroid gland adenomas can be diagnosed by ultrasonography. In 75-80% of patients, diagnosis is made based on ultrasound findings. In order to locate the enlarged parathyroid gland, a radioactive substance called Tc-99 (sestamibi) is administered to the patient for visualization. When no adenomas are identified by any of the abovementioned two methods, computed tomography (CT) or magnetic resonance imaging (MRI) of the neck can be performed.
How Is Diagnosis Made and Treatment Carried Out?
Experts of the field report that parathyroidectomy is the only curative method that is safe and cost-effective. In non-operated patients (asymptomatic patients with slightly elevated blood calcium levels), blood calcium levels and renal functions are tested every 6 months. In these patients, bone mineral density is measured once a year.
Surgical treatment is necessary when hyperparathyroidism causes complaints. Surgery is also needed in the presence of urinary tract stones, peptic ulcers, widespread bone pain, muscle weakness, and high blood pressure.
Surgery should be scheduled in the following asymptomatic patients:
1. Patients younger than 50 years of age
2. Patients who cannot attend regular follow-up visits in the long term
3. Patients having serum calcium levels more than 1 mg/dl than normal
4. Patients with 24-hour urine calcium levels more than 400
5. Patients with at least 30% reduction in renal function
Treatment success rates are 95% or higher when surgery is performed in experienced hands. Open parathyroidectomy (classical method) is performed by exposing and examining all parathyroid glands during surgery in a similar way to goiter surgery. When this type of surgery is planned, it is not necessary for the patient to undergo imaging methods for the demonstration of the pathology. All parathyroid glands will be examined and evaluated during the operation anyway. When multiple-gland disease of the parathyroid gland is considered, when the diagnosis is secondary or tertiary hyperparathyroidism, when there is a suspicion of parathyroid cancer, when imaging methods reveal no diseased parathyroid glands; classical bilateral exploration surgery is performed.
Minimally invasive parathyroidectomy is another type of operation that has started to be performed in recent years following the advances in technology and imaging methods. Minimally invasive parathyroidectomy requires the identification of the diseased parathyroid gland with preoperative ultrasound or scintigraphy before surgery. It is performed by making 1.5-2-cm-incision just above the diseased parathyroid gland.
Rapid assessment of the parathormone levels during surgery is a fast method. Parathyroid hormone levels should be reduced by at least 50% in the second measurement in the sequence of measurements starting after 10 minutes following the excision of the parathyroid adenoma. If no reduction is not achieved, the presence of other adenomas should be investigated. First, the same side of the neck and, if necessary, the other side should be evaluated during surgery. In both ways, it is necessary to determine whether the excised tissue is the parathyroid tissue in the pathological examination.
Postoperative outcomes are associated with the following factors including surgical experience, making a final diagnosis based on preoperative laboratory investigations, finding the location of the diseased gland by imaging methods, confirmation that the diseased gland has been removed based on pathological examination findings, and confirmation by rapid parathyroid hormone level measurements that the diseased parathyroid gland has been excised.