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(Two juvenile iguanas with symptoms of both osteodystrophy fibrosa and nutritional secondary hyperparathyroidism. Note the carpal walking and swollen jaws.)

Edward M. Craft

A calcium deficiency can lead to what is commonly referred to as Metabolic Bone Disease and it is the most commonly seen problem in captive reptiles. This condition is a 100% preventable condition if fed a proper diet. The signs and symptoms most commonly associated with this condition are softness or swelling in the jaws and limbs of the reptile, skeletal deformities or walking on the wrists rather than the toes.

"Metabolic Bone Disease" is NOT a true disease of reptiles. Instead it is a common term given to a group of disorders with similar symptoms. The conditions that are often mis-labeled as MBD are osteodystrophy fibrosa, nutritional secondary hyperparathyroidism, renal secondary hyperparathyroidism, rickets, osteomalacia, and osteoporosis. The conditions most often referred to as MBD are nutritional secondary hyperparathyroidism or hypocalcemia.

(Note the swollen right femur of this juvenile iguana. This may be a symptom of hypocalcemia.)

The reason that calcium is so vital for some reptiles is because it is required for neuromuscular function, blood clotting, and activation of enzymes, heart and muscle contraction as well as bone structure. In order for reptiles, like iguanas, to absorb calcium vitamin D3 is required to help in the absorption process, so when an iguana or other herbivorous or insectivorous reptile fails to receive enough vitamin D3 it can become hypocalcemic despite the fact that it is receiving plenty of calcium in the diet. The same is true if the Cal/Phos ratio of insectivorous lizards is off, since most crickets and mealworms are high in protein and phosphorous and low in calcium. Feeding a proper diet will help to avoid these problems all together along with exposure to NATURAL SUNLIGHT and NOT artificial reptile lights. (See Lighting)

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All rights reserved by Edward M. Craft. Printed in the United States of America. Original Edition 1997