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), 16 discordant (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 < .001. follicle stimulating hormone: r = 0.70, P < .001) with no significant intra-twin differences for gonadotropins, estradiol, and testosterone before or during puberty.

Conclusions: Birthweight has an impact on growth and pubertal maturation. The already decreased height in some low birthweight infants may be further impacted by an early start and fast progression of puberty. The high intra-twin correlation coefficients in our study suggest that puberty and sexual steroids are genetically determined. However, the observed adrenal androgen hypersecretion of the smaller twin during late childhood could have effected pubertal maturation and further decreased near final height.