Metabolic Bone Disease in Reptiles

Some species or individuals are more susceptible to shortcomings in their environments than others. Metabolism of calcium varies with species. For instance, basking lizards, such as the Green Iguana are highly dependent on intense uv light and appropriate temperatures to synthesize vitamin D, whereas a nocturnal gecko may absorb vitamin D from his diet. Not all reptiles are able to use effectively and eliminate safely vitamin D from the digestive tract, and excess supplementation of this or of calcium can greatly upset the balance within the body. The result can be abnormal, irreversible deposition of calcium within the body's organs especially the kidneys that leads to damage or failure.
Kidney or renal failure is a particular problem for Green Iguanas, who are commonly diagnosed with this incurable condition after four or five years of age.

Although many factors contribute to development of the condition, it is known to be directly linked to over-supplementation of vitamins D and minerals (including calcium).
Calcium and vitamin D are present in the diets of wild reptiles in appropriate quantities. Research your pets dietary needs-see related articles. Calcium and vitamin D cannot be given to make up for inadequate uv lighting or incorrect temperatures.
Diets containing excess fat, protein or phosphorus, among other nutrients, will affect the absorption and metabolism of calcium, even if it is present in sufficient quantities in the diet. Again, see relevant husbandry articles.
Commercial diets may be deficient in calcium, high in phosphorus or vitamin D, and may contain other nutrients that negatively affect calcium balance.
MBD is typically seen in: herbivores (plant eaters), such as the Green Iguana who are often fed diets low in calcium and who have very precise uv and temperature requirements; insectivores, such as the Leopard Gecko, who are often fed limited diets low in calcium, such as an all-cricket diet; and omnivores, such as the Bearded Dragon, who also have precise uv and temperature needs, as well as requiring adequate calcium in the diet. True carnivores, such as snakes are less commonly seen with MBD, provided they are fed a whole animal diet, and provided that the prey is mature (ie. the skeleton is fully mineralized with calcium). Carnivores usually receive an adequate calcium concentration and are less dependent on uv light for vitamin D metabolism. The exception may be young animals, or very small snake species, who are fed only calcium poor insects, organ meat (heart, liver, kidney) or meat containing more phosphorus than calcium (that is beef or chicken without the bone). Calcium deficiencies also result from the feeding of too many pinky or fuzzy mice, whose skeletons are not fully calcified. Supplementation may be recommended in these cases. Consult your reptile veterinarian and related articles.