Birthweight Differences in Monozygotic Twins Influence Pubertal Maturation and Near Final Height

Objective To evaluate the influence of unfavorable intrauterine conditions and catch-up growth, we analyzed growth and pubertal maturation in monozygotic twins with significant intra-twin birthweight differences. Study design Prospective longitudinal clinical study of 30 twin pairs at birth, prepubertally at ages 2.1, 4.0, 10.0 years, and mid-/postpubertally at age 14.6 years; 14 pairs were concordant (birthweight difference 1 SDS). Results In 19/30 (63%) pairs, the initially smaller twin started pubertal maturation before the co-twin. In 7/8 (88%) female discordant twin pairs, the initially smaller twin experienced menarche first. Among discordant pairs, highly significant intra-twin differences for height SDS were observed up to 10 years of age, with a further decline between ages 10.0 and 14.6 years. At 10.0 years of age, significant intra-twin differences in mean dehydroepiandrostenedione sulfate were observed in all twin pairs (870.3 vs 1054 ng/mL in the smaller twin, P = .045). This was pronounced in the discordant group: 856.7 vs 1138.2 ng/mL, P = .009. In all twin pairs, highly significant intra-twin correlations were found for gonadotropins during puberty (luteinizing hormone: r = 0.67, P