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Vitamin D Deficiency

Sunshine Delivers Free Vitamin D To Everyone.
Sunshine Delivers Free Vitamin D To Everyone.

What Is Vitamin D?

[dropcap]V[/dropcap]itamin D is the principle regulator of calcium homeostasis (balance) in the body.  This “vitamin” is really a prohormone, meaning it acts like a hormone but is not. Vitamin D does, however, contain cholesterol in its molecular structure like steroid hormones.

The physiological importance of vitamin D encompasses much more than the regulation of bone metabolism although this is a mighty function.

Q: How does vitamin D regulate bone metabolism?

A: In regulation of bone metabolism, vitamin D works in three ways: 1) enables active absorption of calcium from the small intestine, 2) enhances reabsortion of calcium by the kidneys that would otherwise be excreted in urine, and 3) plays an active role in skeletal development and bone mineralization. Mineralization gives strength to living bone tissue.

Vitamin D interacts with receptors within cells to effect transcriptional changes in many cell types including those in gut, bone, breast, prostate, brain, skeletal muscle, and the immune system.1

In regards to the essential role of vitamin D in muscle tissue, it has been recently shown that vitamin D regulates both muscle function and structure of primary myofibers.2

Vitamin D is converted in the body to a molecule that is biologically active. The active form is 1,25-dihydroxyvitamin D, usually referred to as vitamin D3. About 80% comes from sun exposure and the remaining from food.

Vitamin D3 is synthesized in the skin from 7-dehydrocholesterol via photochemical reactions requiring UV light (sunlight). That is, light that contains energy from the sun is incorporated into molecules of  7-dehydrocholesterol in the underlying dermis of skin to make this vitamin. This is why inadequate exposure to sunlight contributes to vitamin D deficiency.

Blood concentration of 25(OH)D is the best indicator of vitamin D status. It reflects vitamin D produced in the skin and that obtained from food and supplements and has a fairly long circulating half-life of 15 days.3

What Is Vitamin D Deficiency In Celiac Disease and/or Gluten Sensitivity?

Sources:
  1. McCarty DE, Chesson AL Jr, Jain SK, Marino AA. The link between vitamin D metabolism and sleep medicine. Sleep Med Rev. 2014 Aug;18(4):311-9. doi: 10.1016/j.smrv.2013.07.001. [↩]
  2. Girgis CM, Mokbel N, Cha KM, Houweling PJ, Abboud M, Fraser DR, Mason RS, Clifton-Bligh RJ, Gunton JE. The vitamin D receptor (VDR) is expressed in skeletal muscle of male mice and modulates 25-hydroxyvitamin D (25OHD) uptake in myofibers. Endocrinology. 2014 Sep;155(9):3227-37 [↩]
  3. http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/ [↩]

Juvenile Autoimmune Thyroid Disease

Trouseau Testing For Tetany.
Trouseau Testing For Tetany. Courtesy Digplanet.

What Is Tetany?

[dropcap]T etany is a painful feature of low blood calcium or low blood magnesium causing hyperexcitability of all nerves which in turn stimulates involuntary sudden, intermittent and repetitious tonic spasms of muscles. Tonic spasms are steady rather than jerky.

Causes include low function of the parathyroid glands which regulate calcium blood levels, vitamin D deficiency which inhibits calcium absorption from the gut that leads to calcium deficiency, and alkalosis.

In alkalosis, the chemical pH (acid/alkaline measure) of blood is too high, or alkaline, which inhibits adequate free calcium ions from being available for cell use.

Q: Why do low blood levels of calcium or magnesium cause muscles to spasm?

A: Calcium controls the readiness of muscle to respond to nerve stimulation. In muscle action, calcium and magnesium are minerals that oppose each other. Calcium allows a muscle to contract while magnesium allows it to relax. Inadequate levels of these opposing minerals affect the ability of muscles to properly function.

A simple test for tetany is called Trouseau’s named after the doctor who developed it. A blood pressure cuff is placed on an upper arm as usual and pumped up to a pressure sufficient to stop blood flow.  The pressure must be held for 3 minutes. A positive result is shown in the above photo of carpopedal spasm: the wrist and hand flexes inward while the fingers extend (opposite of wrist and hand) and the thumb goes against the palm.

What Is Tetany In Celiac Disease and/or Gluten Sensitivity?