Background and rationale: Growth failure is an important and frequent consequence of chronic childhood diseases, such as chronic kidney disease, cancer, and inflammatory bowel disease. A Swedish study encompassing four different nation-complete birth cohorts could show a significant reduction in final adult height in individuals with asthma, correlated with disease severity. However, for most childhood disorders it remains unknown to what extent the condition or its medication affects final height. This is important, because parental concern of their child’s growth is a frequent reason for being referred to a pediatric endocrinologist. Considerable research has been devoted to understanding the genetics of height. The most recent genome-wide association study for height included 5.4 million people – enough to dissect the entire contribution of common genetic variants. Genetics can now explain 45% of the phenotypic variance in height, which makes it possible to predict a child’s adult height with unprecedented precision. Common genetic variants now explain substantially more of the variability than mid-parental height, which have thus far been used as the golden standard height prediction in children. Genetics also has the advantage that it can explain height differences among siblings. Here using genetic data from the UKBiobank (n≈500,000) and the Swedish Twin registry (n≈40,000 with genotype information), we will investigate the impact of chronic pediatric conditions and their treatments on final adult height. Aim and approach: The aim of this study is to investigate the effect of chronic pediatric disease and their drug treatments on final adult height in UKBiobank and the Swedish Twin registry. The overall objective is to determine whether early diagnosis or alternative treatment options could be beneficial for future growth. With the use of longitudinal electronic health records (EHRs), we also aim to identify critical time windows during childhood, when continued growth is most sensitive to illness or drugs. Additionally, we will investigate the interactions between an individual’s genetic profile and growth disruption, i.e. individual sensitivity, and compare effects after stratifying on sex. By studying adult individuals in UKBiobank (n≈ 500,000) and the Swedish Twin registry (n≈40,000 with genotype data) and comparing their genetically predicted height, with their observed final height, we aim to investigate the effects, including the timing of events, of pediatric diseases and treatments on growth. Ultimately, we hope this study will help to determine what gains an early diagnosis or alternative treatment can have on final height, and there by provide clinical guidance.