The parathyroid glands are endocrine glands found in the posterior area in the thyroid gland. Normally, humans have four parathyroid glands. Because of its location, it was only discovered in the 1800's. Despite its close proximity to the thyroid gland, it has a completely differently function in human physiology.
The parathyroid glands secrete the parathyroid hormone or PTH. This hormone is responsible in controlling the calcium levels in the blood and in the bones. This is important because calcium is needed for healthy bones. Calcium is also necessary for synaptic transmission in cells, contraction of muscles and in blood clotting. So when there is a drop in the level of calcium in the blood, the calcium receptors in the parathyroid glands release the hormone to the bloodstream. As the hormones are released, it triggers re-absorption of calcium in the kidneys and in the intestines. In the intestine, the absorption of calcium triggers the activation of vitamin D in the kidney. Vitamin D is responsible for the synthesis of the protein that binds with calcium. This will help the effective absorption of calcium in the blood. In addition to that, the parathyroid hormone suppresses calcium loss thru the urine. When there is an increased level of calcium in the blood, the parathyroid glands decreases its production.
There are problems associated with imbalance of parathyroid hormone. One is hyperparathyroidism and the other is hypoparathyroidism. Hyperparathyroidism results from an increased production of the parathyroid hormone. In most cases, it is caused by a tumor in the parathyroid gland. The excess calcium leaches out from the bones which makes the bone softer and too porous. The bones will be deformed because the areas where calcium used to occupy are now replaced with connective tissues. The increased level of calcium is called hypercalcemia which causes weakness in the skeletal muscles. The excess calcium can also form stones in the kidneys. Hypercalcemia also triggers depression.
Hypoparathyroidism usually occurs when there is less production of PTH. This is usually a result of the removal of the parathyroid gland thru surgery or in some cases, the absence of the parathyroid gland at birth. This leads to hypocalcemia which a serious condition that can lead to tetany and convulsions. This can be life-threatening.
Even though they are small, the parathyroid glands play an important role in the human anatomy. Knowing how the hormones secreted by the glands help us understand how to treat diseases associated with its level of production.