Relationship between metabolic bone disease and bone mineral density measured by dual-energy X-ray absorptiometry in the green iguana (Iguana iguana)

The aim of our work was to study the feasibility of using dual-energy X-ray absorptiometry to obtain reference bone density values in relation to body weight, gender, and metabolic bone disease in the green iguana. The study was performed on 28 animals. The weight, age, and gender of each iguana were recorded. Each lizard was carefully examined and radiographed to detect signs of metabolic bone disease. Blood samples were collected from each animal to evaluate Ca/P and total protein. All animals, both affected (group B; n = 11) and unaffected (group A; n = 17) by metabolic bone disease, were individually scanned using an X-ray densitometer. The regions of interest were the head, lumbar spine, right, and left femur. Statistical analysis was performed separately for each region of interest. Body weight had the strongest relationship with bone density (P<0.01). Within regions of interest, for iguanas of average weight (710g), statistically significant differences between healthy and sick animals were found: head (0.140 vs. 0.090 g/cm(2); P<0.01); lumbar spine (0.164 vs. 0.107 g/cm(2); P<0.01); right femur (0.103 vs. 0.076 g/cm(2); P<0.01); left femur (0.103 vs. 0.078 g/cm(2); P<0.01). Regression equations to obtain reference values of bone density as a function of body weight for animals affected and not affected by metabolic bone disease are provided. Our data indicate that X-ray bone densitometry is an additional tool for studying bone pathophysiology in reptiles.