The parathyroid glands are part of the endocrine system and produces parathyroid hormone (PTH), which regulates the calcium level in the blood. When the calcium level is low, PTH acts on the bones, intestine, and kidneys to increase the calcium in the blood. When the calcium level is high, the PTH should be low. When the calcium level is normal, the PTH should be normal too. The relationship between calcium levels and PTH levels is called a negative feedback loop, meaning they have an inverse relationship.
- There are typically four parathyroid glands, one superior pair and one inferior pair on each side of the neck. Rarely, there can be 5 glands present.
- Normal parathyroid glands are 5 mm, about the size of a grain of rice and weigh between 20 and 40 mg. They are located on the back (posterior) side of the thyroid gland in the low part of the neck around the windpipe and voice box. The parathyroid glands can become overactive and overproduce PTH, causing an increase in blood calcium levels. This is called hyperparathyroidism.
- The most common cause over overproduction of PTH is a benign tumor called an adenoma. The adenoma is an enlarged parathyroid gland and usually weigh between 100 mg and 4 g but can be even larger. Usually there is just one adenoma but sometimes there can be two.
- Less commonly, overproduction is caused by hyperplasia or overgrowth of all four glands.
- Rarely, the cause can be cancer of a parathyroid gland.
- Elevated calcium levels due to hyperparathyroidism can cause many problems including general fatigue; neurologic symptoms such as irritability and lethargy; kidney problems such renal stones and excessive urination; bone and joint pain, muscle weakness, and decreased bone mineral density (osteopenia or osteoporosis); gastrointestinal problems like constipation and nausea. These symptoms are commonly referred to as “painful bones, renal stones, abdominal groans, and psychic moans.” When a patient has any of these signs or symptoms, surgery is recommended. In those who deny symptoms, surgery is recommended if the patient is high risk for developing future problems from hyperparathyroidism: age under 50, calcium levels greater than 10.5 to 11, or decreased kidney function. In those who are asymptomatic and do not have any of the above risk factors, non-surgical observation is usually advised.
- Minimally invasive parathyroidectomy implies that surgery is targeting one specific gland, thus limiting the length of incision and extent of dissection in the neck.
- Traditional surgery involved larger incisions and exploration of all four glands on both sides of the neck. Current technology allows often allows us to identify the diseased gland prior to surgery, and therefore, to minimize the extent of surgery and operating time. Such technology includes the pre-operative neck ultrasound, sestamibi nuclear medicine scans, and specialized four-dimensional CT scan. Many times a patient will undergo a pre-operative injection with radioactive material. A diseased parathyroid gland will have increased uptake of this radioactivity and a probe is used intra-operatively to detect this uptake and localize this gland. Another tool used is intra-operative PTH level. Measuring PTH levels during surgery after removal of an involved gland also allows surgeons to ensure that all of the disease is treated.
- Parathyroid surgery is performed under general anesthesia, and involves an incision in the lower part of the neck in the midline. The size of the incision is usually only 3 cm in length and typically heals with only a faint scar. Occasionally a drain is placed in the wound if the surgeon is concerned about post-operative bleeding. The drain is usually removed 1-2 days after surgery. Overnight hospitalization is required if the patient’s calcium levels are low and need to be monitored.