Nutritional or Metabolic Bone Disease Flashcards
What are some of the functions of calcium?
Neuromuscular function Bone reservoir (regulated by PTH)
What is the likely signalment of an animal with calcium deficiency?
Usually reptiles
What is secondary nutritional hyperparathyroidism?
Low dietary calcium drives higher PTH levels to protect serum Ca levels (takes it from bone). This means bones are often malformed or poorly formed. Most often occurs in growing animals.
Describe the relationship between vitamin D3 and calcium…
Low plasma calcium causes an increase PTH. This in turn increases the amount of inactive Vit D3 converted to active Vit D3 in the kidney. This then goes on to release Calcium from bone and absorb Calcium from the small intestine to increase plasma levels.
What are the names for active vitamin D3?
Calcitriol, 1,25(OH)2D3
How does secondary renal hyperparathyroidism occur?
Occurs due to chronic renal failure (usually in adults). The failing kidneys do not activate enough Vitamin D and do not exctrete enough phosphate (phosphate binds to Ca and forms insoluble CaPO4 so Ca cannot be absorbed) both causing decreased Ca levels. This increases PTH and Ca is resorbed from bones, softening them.
What are the likely clinical signs and history for a reptile with metabolic bone ideas?
History - lethargy, inability to lift trunk/tail, pliant mandible, abnormal posture, weight loss
Cx - joint/limb swelling, decreased muscular tone, atrophy
What are the most likely causes of metabolic bone disease in reptiles?
Low dietary Ca availability, decreased activation/availability of Vit D
How can you diagnose metabolic bone disease in reptiles? What are other DDx?
Rads - swollen bones, poor density, pliant, egg bound, spontaneous fractures.
Blood - hypocalcaemia
DDx - gout, septic arthritis, spinal spondylosis
How can metabolic bone disease in reptiles be treated?
Calcium gluconate, dietary adjustment, UV light (or direct sunlight not through glass).
Ensure to monitor blood calcium.
How is bone formed?
Endochondral ossification: cartilage precursor, then mineralizes, longitudinal bone growth, vertebral bodies, ribs, flat bones - pelvis, failure causes OCD
Intramembranous: direct bone, from periosteum, most flat bones, width of long bones
Explain bone remodelling…
Bone is not dead
Very active (bone production-destruction)
Osteoblast-osteoclast
10% of total skeletal mass renewed per year
It has been suggested up to 30%
Mechanobiology, Wolff’s law: bone morphology adapts in response to increased or decreased mechanical load
What are the non-mechanical influences on boen structure?
Growth hormone: increase rate of longitudinal bones in juvenile, increased bone density in adults
Sex hormones: early neutering delays physeal closure, increased bone length
Leptin: fat tissue, loss of cancellous, increased cortical
What is calcinosis cirumscripta?
Aggregations of calcified nodules in soft tissue
most common in large dog breeds (esp GSD)
Biopsy to ensure it is not a neoplasia
Surgically remove
What is cranio-mandibular osteopathy?
Proliferation of bone in the canine mandible
Leads to discomfort
chewing/eating
Mostly seen in terriers
Unknown cause
No cure, treat pain symptomatically
