Association between P561T polymorphism in growth hormone receptor gene and mandibular prognathism: systematic review and metaanalysis

Objective: Through a systematic review and meta-analysis, the aim this study was evaluating the association between the P561T polymorphism in GHR (rs6184) with skeletal Class III malocclusion in different populations. Methods: A broad search for studies was conducted using the databases: PubMed, Web of Science, Scopus, Cochrane, Google Scholar and Open Grey until December 2018. The study design according to PECOS was: P-Orthodontic patients; E- polymorphism P561T in GHR; C- absence of polymorphism P561T in GHR; O- linear dimension alterations in maxilla and mandibular measurements; S- Cross-sectional studies. The selected studies were qualified by 10-point scoring sheet methodological quality. The subgroups evaluation was performed according to the linear measurements evaluated in two or more studies, as follows: body height, N-S, A’-PTM’, Gn-Go, Pog’-Go, and Co-Go.A fixed effect model was used and the mean differences were performed using the inverse-variance meta-analysis. The I2 (95%) was used to measure statistical heterogeneity between studies, where I2 values of 25%, 50%, and 75% signified low, medium, and high heterogeneity, respectively. Results: The initial search identified 146 studies. After excluding duplicateabstracts, 138 were selected. Seven studies were included in the systematic review. Only one study was classified as having low methodological quality. Three studies were included in the meta-analysis. The meta-analysis demonstrated an association between the Co-Go linear measure and CC genotype (p<0.0001), with a mean difference and confidence interval of 3.79 [2.06, 5.52]. CC was associated with greater mandibularheight. Conclusion: The polymorphism P561T in GHR is associated with Co-Go measurement in Asians, with low level of evidence.