The exon 3 deleted growth hormone receptor gene is associated with small birth size and early pubertal onset in healthy boys.

CONTEXT

The GH/IGF-I axis influences gonadal development and function. Recently, a deletion of exon 3 in the GH receptor gene (GHRd3) has been linked to increased responsiveness to GH.

OBJECTIVE

Our objective was to evaluate the influence of the GHRd3 gene on birth size and pubertal onset.

DESIGN AND SETTING

We conducted a cross-sectional study, part of The COPENHAGEN Puberty Study, at a tertiary center for pediatric endocrinology.

PARTICIPANTS

Participants included 618 healthy boys aged 6.1-19.8 yr.

MAIN OUTCOME MEASURES

We assessed pubertal onset by genital staging and testicular palpation and parental reported birth weight and length. GHR genotypes were determined by multiplex PCR.

RESULTS

Age at onset of genital development (G2+) was significantly earlier in the GHRd3 homozygotes (GHRd3/d3) [10.86 (10.35-11.37) yr, mean (95% confidence interval)] compared with the full-length homozygotes (GHRfl/fl) [11.76 (11.35-12.00) yr, P = 0.002]. The odds ratio of having detectable testosterone levels for a given age was significantly higher in GHRd3/d3 compared with GHRfl/fl group (odds ratio = 3.1; 95% confidence interval = 1.2-8.9; P = 0.036). The GHRd3/d3 group the higher prepubertal IGF-I levels compared with the GHRfl/fl group (9.2% (0.1-18.1%), P = 0.048) after adjustment for IGF-binding protein-3 levels. Lower gestational-age-adjusted birth weight and length were found in the GHRd3/d3 group compared with the GHRfl/fl group and the GHRfl/d3 group, respectively (all P < or = 0.018).

CONCLUSION

The GHRd3/d3 genotype was associated with smaller birth size and earlier age at pubertal onset compared with the GHRfl/fl genotype. Thus, this common polymorphism could play a role for prenatal growth and gonadal development in boys.