PARATHYROID HORMONE ACTIVITY AND RELATED CLINICOPATHOLOGICAL ALTERATIONS IN DOGS AFFECTED WITH CHRONIC KIDNEY DISEASE

Renal secondary hyperparathyroidism (RHPT) is a common complication in humans and dogs affected with chronic kidney disease (CKD). RHPT is promoted mainly by the loss of nephrons and consequent hyperphosphatemia and its severity increases in parallel to the disease. The identification and management of RHPT are suggested in dogs affected with CKD, to establish promptly appropriate treatments and follow the progression of the disease. However, in clinical practice, the determination of parathyroid hormone (PTH) concentration is not routinely due to limited available and validated method and need of radioimmunoassay. In CKD, data about the presence of RHPT in large populations of dogs and the thorough investigation of the association of PTH and other clinicopathological parameters involved in kidney disease are limited. Moreover, in human medicine, PTH has also been identified as an independent prognostic factor in patients affected with CKD and it is also reported that dysregulation of mineral metabolism leading to RHPT is present also in course of acute kidney injury (AKI), as occurs in CKD. Information about these two aspects in dogs is lacking. Hence, this thesis has been divided into two main parts: the first about analytical aspects and the second about clinical data. The first part was focused on the analytical validation of a new immunoenzymatic method validated in humans for the measurement of canine intact PTH and the establishment of the reference interval in healthy dogs. The second main part of this thesis was aimed to investigate the prevalence of RHPT in dogs affected by CKD and AKI, to compare these populations, and to assess the association between PTH and hematological, biochemical, and urinary parameters. Finally, a survival study has been done to elucidate the possible role of PTH as a survival factor in dogs with CKD. The first part of the study has allowed us to successfully validate the method in dogs, which has showed satisfying accuracy and repeatability, and to demonstrate a storage stability of PTH until 6 months at freezing temperature. A reference interval of 1.42-14.59 pg/mL has been established. The second part has allowed us to confirm the relevant presence of RHPT in CKD, also in early stages, and discover several associations between PTH and some parameters such as creatinine and phosphorus, as known, and others not yet identified, such as potassium, hematocrit, and blood pH. RHPT has been identified also in a high percentage of dogs affected with AKI, though the PTH concentrations were not significantly different between AKI and CKD. The survival analysis has revealed that higher concentrations of PTH corresponded to significantly short survival times compared to the lower concentrations, showing a possible prognostic role of PTH in dogs.