endocrinology (primary hyperparathyroidism)

Question 1

what is the physiopathology of primary hyperparathyroidism

Answer 1

primary hyperparathyroidism is characterised by excessive autonomous PTH secretion usually by an adenoma of the parathyroid gland
- most cats with PHPT are affected by single parathyroid gland adenomas

Question 2

how frequent is primary hyperparthyroidism in cats

Answer 2

this is a rare disease in cats

typically seen in older cats (most > 10 years of age)

Siamese cats may be predisposed

Question 3

what are the clinical signs of PHPT

Answer 3

clinical signs are generally vague:
- lethargy
- anorexia
- vomiting
- less commonly PU/PD, weakness, muscle tremors and ataxia
- a palpable cervical mass may be present in up to 50% of cases

Question 4

how is a diagnosis of PHPT made

Answer 4

demonstration of elevated total and ionised calcium concentrations along with high or normal (especially high-normal) PTH concentrations

hypophosphatemia would be predicted in primary hyperparathyroidism but concomitant renal disease is common and this will have a variable effect on phosphate levels

Question 5

what is the treatment for primary hyperparathyroidism

Answer 5

surgical resection of the abnormal tissue is the treatment of choice but close post-operative monitoring is required as atrophy of healthy tissue may lead to temporary hypoparathyroidism

even if a palpable mass is not present, if blood results are consistent with primary hyperphosphatemia, exploratory cervical surgery is warranted