1,25-二羟基维生素D（1,25(OH)2 D）在维持钙离子平衡和骨骼健康以及预防多种疾病（如肿瘤）方面起着关键作用。流行病学数据显示，1,25(OH)2 D及其前体25(OH)维生素D（25(OH)D）浓度过低与多种人类肿瘤的风险增加有关。本研究旨在调查具有可传播性性病瘤（TVT）的犬中25(OH)D、甲状旁腺素（PTH）和免疫标记物浓度。 评估具有TVT（n = 26）和健康犬（n = 30）中25(OH)D、PTH以及多种生化和免疫标记物。与健康犬相比，患有TVT的犬中25(OH)D浓度明显较低。相反，患有TVT的犬中PTH、免疫球蛋白G和白细胞介素（IL）-9浓度较高。其他变量，包括IL-10、γ-干扰素、钙和无机磷，两组之间的差异无统计学意义。 血清25(OH)D浓度降低可能是犬TVT发生的危险因素，但因果关系仍未完全理解。进一步的研究需要阐明25(OH)D在犬TVT中的确切作用，以及维生素D补充是否可作为预防或化疗辅助治疗的有用手段。© 2023 The Authors. Veterinary Medicine and Science published by John Wiley & Sons Ltd.

1,25-Dihydroxyvitamin D (1,25(OH)2 D) is vital in the homeostasis of calcium and bone health as well as in the prevention of many disorders such as neoplasms. Epidemiological data show that low concentrations of both 1,25(OH)2 D and its precursor 25(OH) vitamin D (25(OH)D) are associated with an increased risk of a variety of human tumours.To investigate 25(OH)D, parathormone (PTH) and immunity marker concentrations in dogs with transmissible venereal tumour (TVT).25(OH)D, PTH and various biochemical and immunity markers were evaluated in dogs with TVT (n = 26) and in healthy (n = 30) dogs.25(OH)D concentrations were significantly lower in dogs with TVT in comparison with healthy dogs. In contrast, PTH, immunoglobulin G and interleukin (IL)-9 concentrations were higher in the dogs with TVT. Other variables, including IL-10, interferon γ, calcium and inorganic phosphate, were not statistically different between the two groups.Decreased serum 25(OH)D concentration may be a risk factor for the development of canine TVT; however, cause-and-effect remains incompletely understood. Further studies are required to elucidate the exact role of 25(OH)D in canine TVT and whether vitamin D supplementation may be useful prophylactically or as an adjunct to chemotherapy.© 2023 The Authors. Veterinary Medicine and Science published by John Wiley & Sons Ltd.