Metabolic bone disease is a common but preventable disease seen in pet reptiles. There is no one cause for this disease — the primary problem is a disruption of calcium metabolism that leads to many related problems.
Most often, metabolic bone disease is caused by poor diet and care. Iguanas are very susceptible to metabolic bone disease thanks to their specific light, diet, and environmental needs, but the disease can appear in any reptile.
Without getting too technical, metabolic bone disease results from an improper ratio of calcium to phosphorus in the body. In a normal, healthy reptile, the ratio should be approximately 2:1 (calcium: phosphorus). If calcium levels are low, the body tries to compensate by taking calcium where it can find it — from the bones. Calcium levels also affect muscle contraction and blood clotting.
So what causes a problem in the calcium to phosphorus ratio?
- Too little calcium in the diet.
- Too much phosphorus in the diet.
- Substances in the diet (like oxalates) that impair the body’s absorption of calcium.
- Vitamin D deficiency — vitamin D is essential for calcium metabolism.
- Lack of exposure to UVA and UVB light — exposure to UV rays allows a reptile to manufacture vitamin D.
- Not enough protein in the diet.
- Kidney or liver disease — these can impair the conversion of vitamin D into an active form in the body.
- Small intestine disease — this can impair the absorption of calcium.
- Thyroid disease — this can produce hormones that affect calcium metabolism.
- Cool temperatures — this can impair digestion, changing calcium metabolism.
Metabolic bone disease can be prevented by:
- Providing an appropriate, balanced diet that includes the correct levels of calcium, phosphorus, protein, and other nutrients.
- Providing UVA and UVB light and a day/night cycle.
- Providing proper heat gradients.
- Providing an enclosure of appropriate size — your reptile needs room to exercise.