Metabolic Bone Disease (MBD)

Metabolic bone disease (MBD) is a spectrum of disorders related to a lack (or imbalance) of calcium in the body. The bioavailability of calcium is determined not just by overal calcium in the diet but also the interaction of other vitamins & minerals – most notably vitamin D3 and phosphorus. When the right balance is not available in the diet, calcium is pulled from it’s usual storage – bone mass.

MBD in crested geckos generally takes the form of disfigured  bones, especially in the spine, hips and tail. Weak jawbones are also a sign of MBD, as are swollen limbs. Trembling and overall ill health are caused from the internal turmoil the lack of calcium produces in the body: lack of muscle contractions, loss of liver and kidney function, decrease of nerve function and problems in blood clotting. If a calcium deficiency is not corrected through proper diet or syringe feeding, the gecko will die. Calcium is needed for proper muscle and organ function; the healthy level of calcium in the bloodstream is roughly 1%. Over-supplementation with calcium is rare but possible.

Providing a balanced diet is crucial to prevent this crippling disease.

Signs of MBD

  • Swollen limbs (“Popeye” arms)
  • Swollen jaw
  • Weak jaw that hangs open
  • Underbite or overbite
  • Humped back
  • Irregular spine
  • Kinked tail with multiple zig-zags, especially combined with humped back
  • Shaking, trembling, or twitching of entire body or extremities
  • Organ failure
  • Inability to eat

Look for signs in combination with each other, as taken individually they could be symptoms of something else, such as an injury or genetic condition.

Note that while a crested gecko suffering from MBD can be brought back to health, any deformities in the bone are permanent. Prevention is the best way to avoid crested gecko MBD!

MBD is also known as Nutritional Secondary Hyperparathyroidism (NSHP) within veterinary practices, so your vet may diagnose this in your reptile that is suffering from MBD. In response to low calcium levels (hypocalcemia) the parathyroid glands secrete a hormone that tells the body to start freeing stored calcium from the bone into the blood. It also blocks the absorption of phosphorus in the kidneys so that it can take in more calcium. If the cause of secondary hyperparathyroidism is not nutritional (lack of calcium), then it’s possible the kidneys are in distress, and thereby not converting enough vitamin D or process phosphate, allowing calcium phosphate to continually suck up calcium from the bloodstream. The process loop for these system can snowball if there is any disruption, which creates further deterioration of the process. Hyperparathyroidism is the internal disruption that leads to the physical signs we label as Metabolic Bone Disease.

Frugivorous reptiles like crested geckos are especially susceptible to MBD because of improper supplementation and the use of baby food. Many new keepers are told that babyfood is an acceptable diet and so they don’t supplement and they might not feed anything else. Most fruits are high in phosphorus and low in calcium, which will create a calcium deficit and result in MBD over time. Dusted insects can help, but it’s not going to fix the problem.

Feeding homemade diets or babyfood is not recommended and should be used only as a treat (once a month or so).

Calcium Crash

Breeding females are susceptible to a “calcium crash” as their available calcium is used for producing eggs. Crested geckos have calcium sacs in their mouths to store calcium. Checking them is a good idea if you are acquiring a new crested gecko or have a breeding female. Proper diet again will keep females from a calcium crash which can lead to crested gecko MBD over time.

For details on how to check calcium levels, watch this great calcium sacs video from JB Crestiescrested gecko health information.