Most people have four glands in the neck called the parathyroids, which are typically positioned behind the upper and lower poles of the thyroid. There are two glands on the right and two glands on the left side of the neck. Occasionally the parathyroid glands can be positioned in other locations (ectopic) due to their migrations during embryogenesis. These ectopic glands can be found anywhere from high up in the neck just below the ear to as far down as the heart. Finding ectopic glands can be challenging and requires a surgeon with considerable experience in treating patients with hyperparathyroidism.
The function of the parathyroid glands is to regulate calcium metabolism throughout the body. This function is mediated through parathyroid hormone (PTH) which is made by the parathyroid glands in response to a low level of calcium in the blood. Thus, normally, the blood levels of PTH vary inversely with blood levels of calcium. The higher the calcium level, the lower the expected level of PTH. The lower the calcium level, the higher the expected level of PTH. When the calcium level is low, the parathyroid glands release PTH which works to restore blood calcium levels to normal by increasing absorption from the food that you eat and by mobilizing calcium out of your bones where the vast majority of calcium in your body is stored.