ESPE Abstracts

Background: Low birth weight, unfavourable intrauterine conditions, and post-natal catch-up growth are associated with a subsequent impact on growth and pubertal development. Start of puberty is genetically determined but might be altered due to environmental influences.

Objective and hypotheses: In a longitudinal study we observed genetically identical twins with intra-twin birth-weight (bw) differences from birth until puberty.

Method: 30 pairs of monozygotic twins with intra-twin bw-differences were seen at birth, at a mean of 2.8, 9.8 (prepubertal), and 14.6 (during/post-puberty) years. Birth-weight difference of <1 SDS was defined concordant (n=14), bw-difference >1 SDS was defined discordant (n=16).

Results: Auxiology: In all twin-pairs major catch-up growth occurred from birth to 2.8 years followed by only a slight further catch-up during puberty. However, a significant intra-twin difference for height-SDS remained until the age of 14.6 years (P<0.001). By analysing concordant and discordant twin-pairs separately, we found that concordant twin-pairs remained significantly different only concerning BMI–SDS (P<0.05) but not for height-SDS, whereas in the discordant twins significant differences were observed for height (P<0.001) and BMI–SDS (P<0.01). Puberty: In 63% (19/30) the former lighter twin started puberty before the co-twin, and in only 26% (8/30) the larger twin started first (3/8: no difference reported). In 77% of the girls (10/13) the former lighter twin experienced menarche before the co-twin. In the majority of the boys voice-breaking occurred earlier in the lighter twin. The observed differences were even more pronounced by analysing only the discordant twin-pairs: all lighter girls showed menarche first (median age 12.5 vs 12.8 years).

Conclusion: In this special group of monozygotic twins presenting with different intra-twin bw, we could show that bw has an impact not only on growth but also on puberty. The already impaired height in some low bw infants might be additionally diminished by an early starting and fast progressing puberty.