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Veterinary Care for Your Chameleon

Vitamin D3 and Calcium

by Kenneth L.

Here are the players:
1. Calcium
2. Vitamin D
3. Parathyroid Hormone
4. Calcitonin

Calcium: Calcium is very poorly absorbed through the intestinal mucosa, as are most bivalent cations. When there is excess calcium in the diet much of it binds with phosphate and forms insoluble compounds which are excreted in the feces. Everyone should be aware of the need for calcium in bone formation and muscular contraction, reproduction, etc. (life in general). Too little Calcium causes, among other things, tremors, tetany, and death. **Too much Calcium causes muscles to become sluggish and weak. It has cardiac effects as well as causing obstipation and lack of appetite due to decreased contractility of the intestinal walls.

Vitamin D: Vit D has the job of increasing calcium absorption from the intestinal tract. It also affects both bone deposition AND bone reabsorption. Vitamin D3 is NOT the active substance for these effects. Vit D3 (Cholecalciferol) is formed in the skin by the ultraviolet rays from sunlight. Cholecalciferol is converted by the liver to 1,25 Hydroxycholecalciferol, which in turn is changed through reactions in the kidney to the ACTIVE form; 1, 25 Dihydroxycholecalciferol. **The creation of Hydroxycholecalciferol is limited by a feedback loop, which inhibits the transformation from D3 to Hydroxycholecalciferol. **Vitamin D3 is stored for a long time in the liver, while Hydroxyholecalciferol lasts only a short while. *Now the kidneys take effect and change Hydroxy to Dihydroxycholecalciferol. Remember this when we discuss renal damage. Without the kidneys there are NO active vitamin D effects that can occur. Dihydroxycholecalciferol has its effects upon intestinal epithelium and calcium absorption primarily through the creation of a calcium-binding protein. ** Calcium-binding protein remains in cells for several weeks after the 1,25 Dihyroxycholecalciferol has been eliminated from the body.

Parathyroid Hormone: This hormone causes rapid absorption of calcium salts from the bones in response to decreased calcium in the blood. It also causes phosphate to be lost in the kidneys. Parathyroid Hormone takes many hours to take effect and has a long-term effect.

Calcitonin: Calcitonin DECREASES blood calcium ion concentration. It works very quickly, within minutes. Consider it the opposite of Parathyroid Hormone. **Calcitonin has its greatest effect upon young, rapidly growing animals. **An increase in plasma calcium concentration of about 20% causes immediate two-to-three fold increase in the rate of secretion of Calcitonin.

Back in the 70's and 80's it was very common to see reptiles come in with curved spines, multiple fractures, muscle tremors. Supplements were not commonly used and deaths were common and reproduction of many species was limited. This disease, Metabolic Bone Disease (secondary nutritional hyperparathyroidism) was one of the most common problems seen. Once MBD became a household word and supplements such as Miner-all and RepCal became available MBD, thankfully, became less common. Now we are seeing another distressing trend. I commonly have chams brought in with obstipation, decreased appetites, wasting away, and severe dehydration despite vigilant misting or watering. A common finding in the husbandry goes as follows: " I take great care of her. I water her frequently. I dust her crickets every-other day with Calcium Powder with Vit D3 alternated on off days with a multivitamin powder. When she started becoming depressed I started giving her Neocalglucon and later my vet gave me Baytril". If you only knew how common this scenario is from my perspective it would frighten you.

My question is this: Are we over-supplementing our chams? Here is my reasoning behind the question. 1. Excess calcium causes muscles to become sluggish and weak. It causes decreased appetite and causes obstipation (intractable constipation) due to decreased contractility of the intestinal walls. 2. Excess Vitamin D actually causes ABSORPTION of bone. It actually mimics hyperparathyroidism. 3. Vitamin D causes calcification of bone. Excess Vitamin D causes inappropriate mineralization of organs such as the kidney or soft tissue. Excess Vit D3 and Calcium has been implicated in mineralization of large blood vessels, causing cardiac disease. 4. If we fry the kidneys with excess Vitamin D we cannot get the active form, 1,25 Dihydroxycholecalciferol. Of course, there are many other problems that come along with fried kidneys. 5. The body will only allow so much Hydroxycholecaliferol before the conversion of Vit D3 in the liver is stopped. What happens to the excess Vitamin D3? It is stored in the liver doing no good but potentially causing problems in the future. 6. If the Calcium-binding proteins remain in the cells for weeks after the 1,25 Dihydroxycholecalciferol is gone, why are we redosing two or three times a week? 7. When we over supplement our baby chams with Vit D and Calcium, Calcitonin is secreted which has the job of DECREASING serum calcium. This effect is much more important in young animals. Their young, growing bones are more easily affected by subtle changes in nutritional balances.

SUMMARY: I get way too many consults and patients with signs I feel are suggestive of chronic over-supplementation. It is another case of "A little is good, so a lot must be better" It is not known how much supplementation, if any, is needed for different species. In monkey medicine, for example, Old World monkeys do not need Vit D3 supplements at all while New World monkeys NEED Vit D3 added to their diets. Can we meet their needs better by better gut-loading of our insects and by using a variety of insects in conjunction with proper lighting? Then we can supplement with much less frequency. Please see Susan's Cricket food recipe. I think is well balanced and I have a few of her babies which are remarkable in their health.

The information provided on this site is for your consideration only. You should contact your veterinarian for specific questions concerning your chameleons.