A parathyroid cyst is a sac or pouch of fluid found in the parathyroid glands.
There are two types of the disease: nonfunctioning parathyroid cysts, which display no signs of elevated levels of parathyroid hormone and functioning parathyroid cysts, which exhibit signs of the excessive secretion of parathyroid hormone. The causes and necessary treatments vary according to the type of the disease.
Nonfunctioning parathyroid cysts
To begin with, the parathyroid glands are formed from the pharyngeal pouches (which are equivalent to the gills of fish) in the human embryo. As the embryo develops, the pouches droop in such a way that they are situated behind the thyroid gland. If, in the process of drooping, a duct remains, it is considered to develop into a nonfunctioning parathyroid cyst.
Functioning parathyroid cysts
The causes of functioning parathyroid cysts include bleeding, tumors and infarct (a localized area of dead tissue due to insufficient blood supply commonly resulting from blocked blood vessels).
Nonfunctioning parathyroid cysts
Almost no apparent symptoms are displayed.
Functioning parathyroid cysts
The excessive secretion of parathyroid hormone results in elevated calcium levels in the blood. Once calcium levels in the blood become high, it may cause symptoms such as unusual thirst, nausea and loss of appetite. Patients may also become susceptible to stones in the kidneys or urinary ducts. Arteriosclerosis (thickening and hardening of the walls of arteries), valvular disease of the heart, arthritis (inflammation of joints) and osteoporosis (fragile bones due to reduced bone mass) may develop in some cases.
Tests are performed to measure levels of parathyroid hormone and calcium in the blood in order to determine the type of the disease, nonfunctioning or functioning. The site of a cyst is confirmed through medical examinations such as ultrasonography (echo), computed tomography (CT) and MIBI scintigraphy.
Nonfunctioning parathyroid cysts
The first choice of treatment for a nonfunctioning parathyroid cyst is to puncture the cyst and suck out the fluid inside. In some cases, however, percutaneous ethanol injection therapy (PEIT) is performed.
Functioning parathyroid cysts
Treatments include surgery and a wait-and-see approach and will be determined after consideration of several factors such as calcium levels in the blood, the condition of the bones and past history of stones. Surgery is commonly performed, however, because functioning parathyroid cysts may recur even after disappearing.
