A Comprehensive Cohort Analysis Comparing Growth and GH Therapy Response in IGF1R Mutation Carriers and SGA Children.

CONTEXT: IGF1 receptor mutations (IGF1RM) are rare; however, patients exhibit pronounced growth retardation without catch-up. Although several case reports exist, a comprehensive statistical analysis investigating growth profile and benefit of recombinant human growth hormone (rhGH) treatment is still missing.

OBJECTIVE AND METHODS: Here, we compared IGF1RM carriers (n = 23) retrospectively regarding birth parameters, growth response to rhGH therapy, near final height, and glucose/insulin homeostasis to treated children born small for gestational age (SGA) (n = 34). Additionally, health profiles of adult IGF1RM carriers were surveyed by a questionnaire.

RESULTS: IGF1RM carriers were significantly smaller at rhGH initiation and had a diminished first-year response compared to SGA children (Δ height standard deviation score: 0.29 vs. 0.65), resulting in a lower growth response under therapy. Interestingly, the number of poor therapy responders was three times higher for IGF1RM carriers than for SGA patients (53 % vs. 17 %). However, most IGF1RM good responders showed catch-up growth to the levels of SGA patients. Moreover, we observed no differences in homeostasis model assessment of insulin resistance before treatment, but during treatment insulin resistance was significantly increased in IGF1RM carriers compared to SGA children. Analyses in adult mutation carriers indicated no increased occurrence of comorbidities later in life compared to SGA controls.

CONCLUSION: In summary, IGF1RM carriers showed a more pronounced growth retardation and lower response to rhGH therapy compared to non-mutation carriers, with high individual variability. Therefore, a critical reevaluation of success should be performed periodically. In adulthood, we could not observe a significant influence of IGF1RM on metabolism and health of carriers.