We all know that after bilateral thyroid surgery, a few patients develop hypocalcemia, which manifests as numbness and cramping in the hands and feet, and is caused by damage to the parathyroid glands or their blood supply, which we call hypoparathyroidism and requires long-term calcium supplementation. So, what is the parathyroid glands? As the name implies, the parathyroid glands are the glands located next to the thyroid gland, which is translated as “parathyroid” in Taiwan, and are about the size of a green bean in a normal person. Normal amounts of PTH maintain normal calcium and phosphorus metabolism throughout the body. Once one or more of the parathyroid glands become diseased, such as hyperplasia, adenoma or cancer, they autonomously produce too much PTH, prompting bone destruction and decalcification, resulting in elevated blood calcium and elevated urinary calcium. In moderate cases, osteoporosis and generalized bone pain can occur. In severe cases, bone cysts (similar to bone tumors, called “brown tumors”) can occur, and fractures can easily recur, as can urinary calculi (repeated lithotripsy or stone extraction is ineffective). Constipation, insomnia, hypertension, pancreatitis, and other psychoneurological symptoms or rare manifestations may occur in a small number of patients. The site of onset and clinical presentation are extremely inconsistent and variable, causing hyperparathyroidism to be highly susceptible to misdiagnosis and omission. In fact, once hyperparathyroidism is suspected, the diagnosis is not difficult, with elevated blood calcium, elevated parathyroid hormone, and sometimes decreased blood phosphorus. Experienced ultrasonographers are able to detect abnormally enlarged parathyroid glands in the vicinity of the thyroid gland in the neck, and with pro-parathyroid imaging by isotope technetium, a clear qualitative diagnosis can be obtained. If the qualitative localization diagnosis is clear, the surgery is usually not too difficult, less invasive, and has a good outcome.