The Use Of Vitamin D For Hyperparathyroid And Hypercalcemia

Vitamin D may be used in the treatment of hyperparathyroidism and hypercalcemia; the rationale for this therapeutic approach lies in the physiology of parathyroid hormone and calcium. Always consult with your physician when considering taking vitamins or other supplements.

Parathyroid Hormone and Calcium Physiology

Commonly referred to as PTH, parathyroid hormone is synthesized and released in response to blood calcium levels. For example, when blood calcium decreases, this change is detected by receptors in the parathyroid gland which increase the secretion of PTH. This hormone then travels through the circulation, acting on the kidney, intestine and bone to increase the release of calcium into the blood. As serum calcium levels normalize, PTH secretion decreases and homeostasis is maintained. Because of the effect of PTH on blood calcium, hyperparathyroidism may be associated with hypercalcemia in some cases.

Primary Hyperparathyroidism

Vitamin D may be prescribed for the treatment of a condition known as "primary hyperparathyroidism," in which the parathyroid glands are synthesizing and releasing large amounts of PTH. This results in a massive amount of bone reabsorption as calcium is released into the circulation through the action of PTH. In these cases, the parathyroid gland is overactive and not responsive to the negative feedback mechanisms that normally keep its levels within healthy limits.

Hypercalcemia

Hypercalcemia is a condition characterized by higher than normal calcium levels in the blood; hyperparathyroidism can be a cause of high blood calcium. While calcium plays crucial roles in the function of multiple organ systems, including bones and the brain, excess calcium in the blood can lead to dysfunctional skeletal muscle, heart cell and neuron function. Hypercalcemia has a number of effects including constipation, according to a 2010 article published in the "Journal of Clinical Gastroenterology." High blood calcium levels prevent the smooth muscle of the gut from contracting properly, thus leading to constipation.

The Benefits of Vitamin D

Vitamin D exists in two forms: Previtamin D-3, which is converted to the activated form by the enzyme Vitamin D 25-hydroxylase. Activated vitamin D decreases the synthesis and secretion of parathyroid hormone, according to a 2005 study in "Clinical Nephrology." Consequently, the effect of PTH on calcium reabsorption in the kidney and absorption in the intestine is curbed, reversing the hypercalcemia as well. Specifically, this study examined cases of secondary hyperparathyroidism, which is high PTH secretion with a different cause than "primary hyperparathyroidism."

Considerations

Normally vitamin D is recommended to boost blood calcium; this is because a deficiency of vitamin D may lead to problems absorbing and holding onto calcium in your blood. In addition to inhibiting PTH secretion, vitamin D acts through several of its own mechanisms to increase calcium absorption into the blood. According to a 2007 Columbia University study published in the "Journal of Bone and Mineral Research," vitamin D will act to both lower PTH levels and increases absorption of calcium in in the intestine. These roles may seem incongruous, but they are demonstrating the central role of vitamin D in the balance of the metabolic systems.