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

J Vet Intern Med. 2021 May;35(3):1265-1273. doi: 10.1111/jvim.16143. Epub 2021 May 15.


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.

Keywords: FGF-23; calcitriol; hyperadrenocorticism; parathyroid hormone; urinary calcium excretion; vitamin D.

MeSH terms

  • Animals
  • Calcium
  • Cross-Sectional Studies
  • Cushing Syndrome* / veterinary
  • Dog Diseases*
  • Dogs
  • Homeostasis
  • Parathyroid Hormone
  • Phosphates
  • Prospective Studies


  • Parathyroid Hormone
  • Phosphates
  • Calcium