Are vitamin D and vitamin D receptor levels different in children with developmental dysplasia of the hip?

INTRODUCTION: Developmental dysplasia of the hip (DDH) is a common disorder and associated with significant morbidity of the hip joint. Several risk factors have been identified for DDH. The aim of this study is to investigate whether vitamin D and vitamin D receptor (VDR) levels differ in children with DDH and whether they have an effect on DDH development. MATERIALS AND METHODS: A total of 40 (17 males, 23 females; 9 right hips, 16 left hips, 15 bilateral hips) children who were treated for developmental dysplasia and 40 (23 males, 17 females) healthy children without any musculoskeletal system and metabolic disorders were included in this study between January and June 2019. Blood samples from the DDH and control groups of children were collected to measure the serum levels of vitamin D, VDR, calcium (Ca), phosphorus (P), and alkaline phosphatase (ALP). The levels of Ca, P, and ALP were analyzed using the automated standard spectrophotometric laboratory method. The levels of vitamin D and VDR in the samples were analyzed using enzyme-linked immunoassay. RESULTS: There were no significant differences in the serum levels of Ca, P, ALP, and vitamin D between the DDH and healthy groups (Ca 9.96 ± 0.47 vs. 9.92 ± 0.48 mg/dL, respectively, p = 0.721; P 5.3 ± 0.94 vs. 4.82 ± 0.88 mg/dL, respectively, p = 0.23; ALP 252.22 ± 170.15 vs. 245.3 ± 130.93 U/L, respectively, p = 0.839). However, serum VDR levels were significantly lower in children in the DDH group (5.77 ± 3.51 ng/mL) than in the healthy control group (9.25 ± 6.43 ng/mL) (p = 0.004). CONCLUSIONS: In conclusion, we believe that low VDR levels can affect DDH regardless of the serum levels of Ca, P, ALP, and vitamin D. More comprehensive studies involving parents are needed to understand whether VDR levels mediate genetic transmission in DDH or not.