Objectives

To assess the effects of hyperadrenocorticism on parathyroid hormone (PTH) secretion in the dog.

Materials & Methods

PTH was measured in 68 dogs with confirmed hyperadrenocorticism that did not have azotaemia. Routine biochemical screens were obtained from all dogs and ionised calcium was measured in 28 of the dogs. The results obtained were compared to an age and weight matched group of twenty hospital patients that did not have hyperadrenocorticism or azotaemia.

Results

It was found that there was significant difference between the PTH, phosphate and albumin concentrations between the two groups. Calcium concentrations were not significantly different. A large proportion (92%) of the dogs with hyperadrenocorticism had PTH concentrations that were greater than the established laboratory reference range (10-60 pg/ml). Furthermore 23 dogs had PTH concentrations that were greater than 3 times the upper limit of the reference range (180 pg/ml). There were significant but weak correlations between the PTH and basal cortisol concentrations and the phosphate and post-ACTH cortisol concentrations.

Conclusion

Increased PTH is likely to be a factor in the pathogenesis of those clinical signs of hyperadrenocorticism that are associated with defects in calcium homeostasis (e.g., calcinosis cutis).