Serum intact parathyroid hormone levels in cats with chronic kidney disease / Avaliação das concentrações séricas de paratormônio intacto em gatos com doença renal crônica

Chronic kidney disease (CKD) is frequently observed in cats and it is characterized as a multisystemic illness, caused by several underlying metabolic changes, and secondary renal hyperparathyroidism (SRHPT) is relatively common; usually it is associated with the progression of renal disease and poor prognosis. This study aimed at determining the frequency of SRHPT, and discussing possible mechanisms that could contribute to the development of SRHPT in cats at different stages of CKD through the evaluation of calcium and phosphorus metabolism, as well as acid-base status. Forty owned cats with CKD were included and divided into three groups, according to the stages of the disease, classified according to the International Renal Interest Society (IRIS) as Stage II (n=12), Stage III (n=22) and Stage IV (n=6). Control group was composed of 21 clinically healthy cats. Increased serum intact parathyroid hormone (iPTH) concentrations were observed in most CKD cats in all stages, and mainly in Stage IV, which hyperphosphatemia and ionized hypocalcemia were detected and associated to the cause for the development of SRHPT. In Stages II and III, however, ionized hypercalcemia was noticed suggesting that the development of SRHPT might be associated with other factors, and metabolic acidosis could be involved to the increase of serum ionized calcium. Therefore, causes for the development of SRHPT seem to be multifactorial and they must be further investigated, mainly in the early stages of CKD in cats, as hyperphosphatemia and ionized hypocalcemia could not be the only factors involved.(AU)

A doença renal crônica (DRC) em gatos é frequentemente observada e caracteriza-se como alteração multissistêmica, causada por alterações metabólicas, e o hiperparatireoidismo secundário renal (HPTSR) seria o mais comum e usualmente está associada com progressão da doença renal e mau prognóstico. Esse estudo teve como objetivo determinar a frequência do HPTSR, e discutir os possíveis mecanismos que podem contribuir para o desenvolvimento de SRHPT em gatos em diferentes estágios de DRC, pela avaliação do metabolismo do cálcio e fósforo, bem como do equilíbrio ácido-base. Quarenta gatos com DRC foram divididos em três subgrupos, de acordo com a classificação proposta pela International Renal Interest Society (IRIS), Estágio II (n=12), Estágio III (n=22) e Estágio IV (n=6). O grupo-controle foi composto por 21 gatos clinicamente saudáveis. O aumento das concentrações séricas de paratormônio intacto (PTHi) foi observado na maioria dos casos, mas principalmente no Estágio IV, no qual a hiperfosfatemia e a hipocalcemia ionizada parecem estar associadas ao desenvolvimento do HPTSR. No entanto, nos Estágios II e III, observou-se hipercalcemia ionizada, sugerindo que, nestes estágios, o desenvolvimento do HPTSR possa estar associado a outros fatores, e a acidose metabólica pode estar envolvida com o desenvolvimento de hipercalcemia ionizada. Assim, outros fatores, além da hiperfosfatemia e da hipocalcemia ionizada, possam estar envolvidos com o desenvolvimento do HPTSR, principalmente nos estágios iniciais da DRC. Futuros estudos são necessários para uma melhor compreensão da fisiopatologia do HPTSR em gatos.(AU)

Serum intact parathyroid hormone levels in cats with chronic kidney disease / Avaliação das concentrações séricas de paratormônio intacto em gatos com doença renal crônica

Chronic kidney disease (CKD) is frequently observed in cats and it is characterized as a multisystemic illness, caused by several underlying metabolic changes, and secondary renal hyperparathyroidism (SRHPT) is relatively common; usually it is associated with the progression of renal disease and poor prognosis. This study aimed at determining the frequency of SRHPT, and discussing possible mechanisms that could contribute to the development of SRHPT in cats at different stages of CKD through the evaluation of calcium and phosphorus metabolism, as well as acid-base status. Forty owned cats with CKD were included and divided into three groups, according to the stages of the disease, classified according to the International Renal Interest Society (IRIS) as Stage II (n=12), Stage III (n=22) and Stage IV (n=6). Control group was composed of 21 clinically healthy cats. Increased serum intact parathyroid hormone (iPTH) concentrations were observed in most CKD cats in all stages, and mainly in Stage IV, which hyperphosphatemia and ionized hypocalcemia were detected and associated to the cause for the development of SRHPT. In Stages II and III, however, ionized hypercalcemia was noticed suggesting that the development of SRHPT might be associated with other factors, and metabolic acidosis could be involved to the increase of serum ionized calcium. Therefore, causes for the development of SRHPT seem to be multifactorial and they must be further investigated, mainly in the early stages of CKD in cats, as hyperphosphatemia and ionized hypocalcemia could not be the only factors involved.

A doença renal crônica (DRC) em gatos é frequentemente observada e caracteriza-se como alteração multissistêmica, causada por alterações metabólicas, e o hiperparatireoidismo secundário renal (HPTSR) seria o mais comum e usualmente está associada com progressão da doença renal e mau prognóstico. Esse estudo teve como objetivo determinar a frequência do HPTSR, e discutir os possíveis mecanismos que podem contribuir para o desenvolvimento de SRHPT em gatos em diferentes estágios de DRC, pela avaliação do metabolismo do cálcio e fósforo, bem como do equilíbrio ácido-base. Quarenta gatos com DRC foram divididos em três subgrupos, de acordo com a classificação proposta pela International Renal Interest Society (IRIS), Estágio II (n=12), Estágio III (n=22) e Estágio IV (n=6). O grupo-controle foi composto por 21 gatos clinicamente saudáveis. O aumento das concentrações séricas de paratormônio intacto (PTHi) foi observado na maioria dos casos, mas principalmente no Estágio IV, no qual a hiperfosfatemia e a hipocalcemia ionizada parecem estar associadas ao desenvolvimento do HPTSR. No entanto, nos Estágios II e III, observou-se hipercalcemia ionizada, sugerindo que, nestes estágios, o desenvolvimento do HPTSR possa estar associado a outros fatores, e a acidose metabólica pode estar envolvida com o desenvolvimento de hipercalcemia ionizada. Assim, outros fatores, além da hiperfosfatemia e da hipocalcemia ionizada, possam estar envolvidos com o desenvolvimento do HPTSR, principalmente nos estágios iniciais da DRC. Futuros estudos são necessários para uma melhor compreensão da fisiopatologia do HPTSR em gatos.

Serum ionized calcium in dogs with chronic renal failure and metabolic acidosis.

BACKGROUND: Chronic renal failure (CRF) is a common disease in dogs, and many metabolic disorders can be observed, including metabolic acidosis and calcium and phosphorus disturbances. Acidosis may change the ionized calcium (i-Ca) fraction, usually increasing its concentration. OBJECTIVE: In this study we evaluated the influence of acidosis on the serum concentration of i-Ca in dogs with CRF and metabolic acidosis. METHODS: Dogs were studied in 2 groups: group I (control group = 40 clinically normal dogs) and group II (25 dogs with CRF and metabolic acidosis). Serum i-Ca was measured by an ion-selective electrode method; other biochemical analytes were measured using routine methods. RESULTS: The i-Ca concentration was significantly lower in dogs in group II than in group I; 56% of the dogs in group II were hypocalcemic. Hypocalcemia was observed in only 8% of dogs in group II when based on total calcium (t-Ca) concentration. No correlation between pH and i-Ca concentration was observed. A slight but significant correlation was detected between i-Ca and serum phosphorus concentration (r = -.284; P = .022), as well as between serum t-Ca and i-Ca concentration (r = .497; P < .0001). CONCLUSION: The i-Ca concentration in dogs with CRF and metabolic acidosis varied widely from that of t-Ca, showing the importance of determining the biologically active form of calcium. Metabolic acidosis did not influence the increase in i-Ca concentration, so other factors besides acidosis in CRF might alter the i-Ca fraction, such as hyperphosphatemia and other compounds that may form complexes with calcium.