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Parathyroid Disease & Renal Disease

The parathyroid glands secrete a hormone that keeps blood calcium levels in check. Calcium is essential to muscle and nerve control. Healthy kidneys secrete some calcium in the urine, but most of the secreted calcium is reabsorbed. Renal disease, a failure of the kidneys to function properly, leads to increased calcium in the urine, lowering calcium in the blood. The parathyroid glands react to this by secreting more hormone than normal, a condition called secondary parathyroidism. Untreated, this condition leads to bone loss and higher-than-normal blood calcium levels.

  1. Parathyroid Glands

    • The parathyroid glands are four glands that can be found in humans behind the thyroid gland around the larynx. The parathyroid glands secrete a hormone called parathyroid hormone (PTH). PTH is responsible for regulating the level of calcium in the blood by promoting the release of calcium by the bones. When too much PTH is released, a condition called hyperparathyroidism, calcium levels in the blood increase. People with this condition feel run down or exhibit irritability and sometimes insomnia.

    Kidneys

    • The renal system is made up of the kidneys, which are two organs in the back of the abdomen that help filter out water-soluble chemicals from the blood and then excrete them in urine. Typically, the kidneys will filter out elements that are toxic to humans. However, elements necessary for life sometimes get through. A complex system in the kidneys reabsorbs these elements from urine and returns them to the blood. Calcium is one such element.

    Renal Disease

    • Certain conditions like diabetes and high blood pressure destroy the kidneys' ability to properly filter the blood. As a result, calcium and other essential elements escape into the urine. This causes a drop in blood calcium levels as the kidneys are unable to reabsorb all the calcium that is being excreted.

    Secondary Hyperparathyroidism

    • When calcium levels in the blood decrease, the parathyroid glands release PTH. PTH causes the decalcification of the bones in order to increase the levels of calcium in the blood. This process continues in a cycle as the calcium released from the bones also escapes through the kidneys, which causes more PTH to be released. The consequences of this are low calcium levels in the blood and decreased bone mass. Calcium is essential in the transmission of nerve impulses to the muscles. Bones are essential in maintaining the structure of the body and the protection of vital organs. This overactive action of the parathyroid glands is termed "secondary hyperparathyroidism" because it is caused in response to a primary disease, kidney disease, and not because of something inherently wrong with the parathyroid glands.

    Diagnosis and Treatment

    • Diagnosis of hyperparathyroidism involves testing the levels of PTH in the blood and calcium in urine. If the levels of calcium are found to be abnormally low in the blood and high in the urine, the health care provider may look to the kidneys for the cause. If kidney function is normal, other diseases that cause a drop in blood calcium or increase in urine calcium are also pursued. In primary hyperparathyroidism, the only option to treat is to remove the glands. In secondary hyperparathyroidism, the kidney disease is treated in order to prevent more calcium from escaping. That should correct the PTH levels back to normal.

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