Nutritional hyperparathyroidism in the puppy: normal calcium
4-month-old mixed-breed puppy fed home-cooked minced meat and rice since weaning, with no supplements. Lameness in several limbs, pain on palpation of the long bones and reluctance to move. Radiographs show thin cortices and low bone density, with physes of normal width. Bloods:
| Parameter | Result | Reference |
|---|---|---|
| Total calcium | 10.4 mg/dL | 9.0–11.8 |
| Phosphorus | 7.9 mg/dL | 2.5–6.0 (adult) |
| Alkaline phosphatase | 290 U/L | 20–155 (adult) |
Which statement about these results is correct?
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A. Normal serum calcium rules out nutritional secondary hyperparathyroidism
PTH keeps serum calcium within range at the expense of bone, so normal calcium is to be expected and does not rule out the disease.
B. The raised alkaline phosphatase confirms metabolic bone disease
Growing puppies have higher alkaline phosphatase (bone isoenzyme) and phosphorus than adults; against adult ranges, these values are not specific.
C. Normal calcium does not rule it out: the low-calcium, high-phosphorus diet stimulates PTH, which maintains blood calcium by mobilising it from bone
Correct. Meat is high in phosphorus and contains almost no calcium. Increased PTH corrects serum calcium at the expense of bone resorption, causing osteopenia, pain and pathological fractures. Diagnosis is based on the diet, radiographs and, if needed, PTH.
D. A bone biopsy is essential to confirm it
It is not necessary: the dietary history, clinical signs and generalised osteopenia with normal physes are highly suggestive, and the response to dietary correction supports the diagnosis.
lightbulb Key takeaway
Correct the diet with a complete puppy food (or a home-made diet formulated by a nutritionist), restrict activity and control pain while the bone remineralises over weeks. Normal-width physes distinguish it from rickets, in which they are widened. Always ask what the puppy eats: unformulated 'natural' meat diets are the usual cause.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.