Vitamin D Toxicity & Hyperparathyroidism

Vitamin D is vital for the maintenance of healthy levels of calcium in your bloodstream and maintaining healthy vitamin D levels is also important. If you have too much vitamin D in your bloodstream a condition known as vitamin D toxicity, abnormally high calcium levels, can result. Abnormally low levels of vitamin D can cause secondary hyperparathyroidism, as your body tries to maintain adequate calcium levels in the absence of vitamin D.

Vitamin D

Vitamin D is one of four fat-soluble vitamins that your body requires. Fat-soluble vitamins are stored in your body, whereas water-soluble vitamins are excreted in your urine. The fat-soluble vitamins are A, D and E, but vitamin D is unique among these vitamins in that your body synthesizes it, rather than obtaining it strictly through dietary sources. Your epidermis creates vitamin D when ultraviolet-B, or UVB, radiation from the sun hits your skin. It is not naturally present in a wide range of foods, but in many cases has been added to fortify processed foods. Vitamin D is essential for absorbing calcium through your intestines, reabsorbing it via your kidneys and transferring it from your bones when blood levels of calcium fall too low.

Effects of Vitamin D Toxicity

Debate remains over how much vitamin D results in toxicity, but be assured that your body won't synthesize toxic amounts of vitamin D in response to sun exposure. It's also doubtful you'll get enough vitamin D from dietary sources to cause toxicity, according to the University of Maryland Medical Center. Vitamin D supplements are the most likely source of vitamin D toxicity, and in your quest to ensure you're getting enough of this nutrient, it's important not to overdo it. The side effects of too much vitamin D include a metallic taste in the mouth, declining appetite, weight loss, bone pain, vomiting and muscle dysfunction. Vitamin D toxicity can cause kidney stones and organ calcification, according to the Linus Pauling Institute. The tolerable upper limit of vitamin D for adults 19 and older is 4,000 IU daily.

Vitamin D and Hyperparathyroidism

If the pendulum swings in the other direction and your vitamin D levels fall too low, you may experience hyperparathyroidism. This occurs when a vitamin D deficiency causes a decline in calcium absorption. Your endocrine system senses the drop in serum calcium levels and responds by secreting more parathyroid hormone, which causes your body to steal calcium from your bones, increase reabsorption of calcium from your kidneys and increase intestinal absorption of calcium, according to Gary Thibodeau, Ph.D., author of "The Human Body in Health and Disease." This in turn can cause hypercalcemia, with subsequent confusion, anorexia and fatigue, which can lead to shock, kidney failure and death.

Considerations

Getting too much, or too little vitamin D can be dangerous to your health. Vitamin supplements can have fatal adverse effects if taken improperly. Fortunately vitamin D is easy to obtain by exposing your skin to sunlight for a brief period about three times per week. If you have dark skin or live in a climate that doesn't receive much sunshine, your needs may vary. Consult your doctor before taking vitamin D supplements.