Nutritional Secondary Hyperparathyroidism

Nutritional Secondary Hyperparathyroidism

Young growing animals have a greater requirement for calcium than adults do to achieve normal mineralization of cartilage and bone.

Nutritional secondary hyperparathyroidism develops if there is a calcium deficiency in the diet, or an increase in dietary phosphorus combined with a normal or decreased calcium, or a deficient intake of vitamin D.

The condition is mainly seen in dogs and cats (especially kittens of Oriental breeds) that are fed all-meat diets or all-grain diets. Meat, offal and cereals are deficient in calcium and rich in phosphorus.

Pathogenesis:

An increased plasma phosphorus level produces a reciprocal fall in the plasma calcium concentrations.

Chronic low calcium levels stimulated the release of parathyroid hormone.

This process of increased parathyroid hormone eventually will cause weakening of the bone resulting in both bone pain and pathological fractures (fractures following relatively minor events such as jumping from a sofa.

Clinical Signs:

Usually seen in dogs and cats under 6 months of age.

Lameness

Reluctance to move

Bone and joint pain

Unstable or wobbly gait if there are fractures of the vertebrae.

Deformities of the long bones resulting from pathological fractures.

Deterioration of posture, with splaying of the toes and sinking of the carpi and tarsi.

Chronic constipation can develop if there is a narrowing of the pelvis as a result of pathological fractures.

Diagnosis:

The disorder can be suspected from dietary history of affected animals.

Radiographs show a generalized bone density, and the walls of the bones appear thinner than normal. The reduction of bone density will not be apparent until there is at least 30% reduction in the mineral content of the bone.

Pathological fractures may be present.

Laboratory findings:

-Low to normal serum calcium levels

-Normal to high phosphorus levels

-Increased serum alkaline phosphatase

-Increase plasma parathyroid hormone level

Treatment:

Correct the dietary imbalance by feeding nutritionally balanced pet food

Animals with skeletal deformities should be confined for the first four weeks of dietary correction to prevent further injury and to limit any progression of skeletal deformity. Corrective osteotomies of long bones can be considered when the skeleton has mineralized to a sufficient level.

Animals with spinal injuries may never recover

Analgesics can be used for pain relief-avoid corticosteroids, which will further lower plasma calcium levels

Many animals will remain stunted in growth even with dietary correction

Prevention:

All young dogs and cats should be fed a balanced diet that contains adequate, yet not excessive, amounts of calcium, phosphorus, and vitamin D. This is best provided in the form of a nutritionally balanced pet food

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