Calcium and phosphate homeostasis in dogs with newly diagnosed naturally occurring hypercortisolism

Phosphocalcic metabolism and its potential association with biomarkers of kidney disease in dogs with spontaneous hyperadrenocorticism

The pathogenesis of increased serum phosphate concentration and proteinuria in dogs with spontaneous hyperadrenocorticism (HAC) is unclear. A potential link between proteinuria and calcium/phosphate metabolism has never been studied in dogs with HAC. The aims of the study were: (1) To evaluate calcium/phosphate metabolism in dogs with spontaneous HAC and compare to healthy dogs as well as to dogs with non-HAC illness; (2) to look for associations between markers of calcium/phosphate metabolism and biomarkers of kidney disease in dogs with HAC. Fifty-four dogs were included in the study, classified as HAC (n=27), non-HAC disease (n=17), and healthy (n=10). Serum calcium, phosphate, 25(OH)Vitamin D, 1,25(OH)2Vitamin D, plasma intact parathyroid hormone concentration (iPTH), FGF23, and urinary fractional excretion of calcium and phosphate were evaluated in all dogs at diagnosis and compared between each group. The correlation between these variables and urine protein-to-creatinine ratio (UPC) and urinary N-acetylglucosaminidase-to-creatinine ratio (uNAG/C) was evaluated in the HAC group. Medians [range] of serum phosphate concentration, urinary fractional excretion of calcium (FE(Ca)), and iPTH were significantly higher in dogs with HAC than in dogs with non-HAC illness (P<0.01) and healthy dogs (P<0.01). Increased 1,25(OH)2Vitamin D/25(OH)Vitamin D was also observed (P<0.001). In HAC group, UPC was significantly negatively correlated with 25(OH)Vitamin D (r(s): -0.54; P<0.01). Urinary NAG/C was significantly positively correlated with serum phosphate (r(s): 0.46; P=0.019). Increased serum phosphate, urinary excretion of calcium, and hyperparathyroidism were observed in dogs with HAC. Vitamin D metabolism may be shifted towards increased 1-alpha hydroxylation.

Pamidronate-induced irreversible symptomatic hypocalcemia in a dog with hypercalcemia after glucocorticoid withdrawal: a case report

BACKGROUND

Pamidronate is used for the treatment of hypercalcemia. However, a rare but potential adverse event of pamidronate treatment is hypocalcemia. This report describes an unusual case of severe, irreversible hypocalcemia after a single injection of pamidronate for the treatment of hypercalcemia due to glucocorticoid withdrawal in a dog.

CASE PRESENTATION

An 11-year-old castrated male Maltese dog presented with anorexia, vomiting, and diarrhea (day 0). The patient had calcinosis cutis throughout the body, calcification of intraabdominal organs, mild azotemia, and severe hypercalcemia. The severe calcification was attributed to long-term glucocorticoid administration, which was discontinued 1 month before presentation. Fluid therapy, diuretics, calcitonin, and a single intravenous injection of pamidronate were used for the treatment of hypercalcemia. On day 14, normocalcemia was achieved, but renal failure occurred. On day 20, severe and irreversible hypocalcemia occurred, and on day 42, the patient was euthanized at the owner's request because of worsened hypocalcemia and renal failure.

CONCLUSIONS

Although hypocalcemia is an extremely rare adverse event of bisphosphonate treatment, bisphosphonates like pamidronate can result in potentially life-threatening conditions according to the patient's underlying conditions. Therefore, the patient's condition should be closely monitored and any underlying conditions should be carefully evaluated before initiating the treatment for hypercalcemia using pamidronate.

Calcium and phosphate homeostasis in dogs with newly diagnosed naturally occurring hypercortisolism

Background

Hypercortisolism affects calcium and phosphate metabolism in dogs; however, the exact mechanisms are not completely understood.

Objectives

To evaluate circulating concentrations of whole parathormone (wPTH), 25‐hydroxyvitamin D (25‐(OH)D), calcitriol, and fibroblast growth factor‐23 (FGF‐23) in dogs with naturally occurring hypercortisolism (NOHC) and healthy dogs, and their association with calcium and phosphate homeostasis.

Animals

Twenty‐three client‐owned dogs with NOHC, and 12 client or staff‐owned healthy dogs.

Methods

Prospective cross‐sectional study. The circulating concentrations of total calcium, ionized calcium (iCa), phosphate, wPTH, 25‐(OH)D, calcitriol and FGF‐23, and the urinary fractional excretion of phosphate (FEP) and calcium (FECa) were compared between dogs with NOHC before treatment and healthy dogs.

Results

Dogs with NOHC had higher mean serum phosphate concentrations (4.81 mg/dL, SD ± 0.71 vs 3.86 mg/dL, SD ± 0.60; P < .001), median FECa (0.43%, range, 0.03‐2.44 vs 0.15%, range, 0.06‐0.35; P = .005), and median serum wPTH concentrations (54.6 pg/mL, range, 23.7‐490 vs 24.6 pg/mL, range, 5.5‐56.4; P = .003) as compared to the controls. Circulating concentrations of total calcium, iCa, and calcitriol and the FEP did not differ between groups, whereas the serum 25‐(OH)D concentrations were lower in dogs with NOHC as compared to the controls (70.2 pg/mL, SD ± 42.3 vs 106.3 pg/mL, SD ± 35.3; P = .02). The dogs with NOHC had lower plasma FGF‐23 concentrations than controls (316.6 pg/mL, range, 120.8‐575.6 vs 448.7 pg/mL, range, 244.8‐753; P = .03).

Conclusions and Clinical Importance

Urine loss of calcium and hyperphosphatemia could contribute to the adrenal secondary hyperparathyroidism.