Background: GH therapy during the transition period is important for somatic maturation. Identification of factors associated with low IGF-I levels may be useful in optimising GH replacement therapy.
Objectives: To explore the prevalence and determinants of insufficient GH replacement during transition
Methods: Childhood-onset GH deficient (CO-GHD) patients (n=65) who stopped therapy, and were started on adult GH dose during transition (age < 26 yrs) were identified from KIMS (Pfizer International Metabolic Study) database in UK. The IGF-I levels while off therapy (IGF-I-Baseline), first available levels during therapy (IGF-I-Response), and after 6 months of starting GH (IGF-I titrated) were used for analysis. IGF-I standard deviation scores (SDS) were calculated using age and gender-specific normative data.
Results: The mean (± SD) IGF-I-titrated SDS (+ 0.22 ± 0.15) was similar to population means (P=0.30). However, insufficient (IGF-I SDS <−2) and suboptimal (IGF-I SDS −2 to 0) levels were observed in 10.5% and 31.6% of patients respectively. Higher GH doses were associated with female gender (P=0.046) (Table) and oestrogen therapy (0.54 ± 0.22 mg vs 0.36 ± 0.11 mg, P=0.022). IGF-I-Response SDS was closely associated with IGF-I-Baseline SDS (r=0.75, P<0.0001) independent of the GH dose (r=0.34, P=0.006). Lower IGF-I-Baseline SDS was related to female gender (−3.53 ± 1.85 vs −2.34 ± 1.67, P=0.010) and oestrogen therapy (−4.12 ± 1.99 vs −2.42 ± 1.43, P=0.025). Younger age was related to lower increments of IGF-I SDS during GH treatment(r=0.27, P=0.041).
Conclusions: Suboptimal IGF-I levels suggests that a proportion CO-GHD patients may be receiving insufficient GH replacement during transition. Lower IGF-I SDS while off therapy, female gender, oestrogen therapy, and younger age adversely affect IGF-I levels during GH therapy. Further studies are required to establish the optimal levels of GH replacement during transition.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: Declaration of Funding: This work was supported by an Independent Investigator Research grant from UK KIGS KIMS board (Pfizer).