Influence of Prenatal Environment on Androgen Steroid Metabolism In Monozygotic Twins With Birthweight Differences.

OBJECTIVE: Although low birthweight (bw) and unfavorable intrauterine conditions have been associated with metabolic sequelae in later life, little is known about their impact on steroid metabolism. We studied genetically identical twins with intra-twin bw-differences from birth to adolescence to analyze the long-term impact of bw on steroid metabolism. METHODS: 68 monozygotic twin pairs with a bw-difference of <1 standard deviation score (SDS; concordant; n = 41) and ≥1 SDS (discordant; n = 27) were recruited. At 14.9 years (mean age), morning urine samples were collected and analyzed with gas chromatography-mass-spectrometry. RESULTS: No significant differences were detected in the concordant group. In contrast, in the smaller twins of the discordant group, we found significantly higher concentrations not only of the dehydroepiandrosterone sulfate (DHEAS) metabolite 16α-OH-DHEA (P = 0.001, 656.11 vs 465.82 µg/g creatinine) but also of cumulative dehydroepiandrosterone and downstream metabolites (P = 0.001, 1650.22 vs 1131.92 µg/g creatinine). Relative adrenal (P = 0.002, 0.25 vs 0.18) and overall androgen production (P = 0.001, 0.79 vs 0.65) were significantly higher in the formerly smaller discordant twins. All twin pairs exhibited significant intra-twin correlations for all individual steroid metabolites, sums of metabolites, indicators of androgen production, and enzyme activities. Multiple regression analyses of the smaller twins showed that individual steroid concentrations of the larger co-twin were the strongest influencing factor among nearly all parameters analyzed. CONCLUSION: In monozygotic twin pairs with greater intra-twin bw-differences (≥1 SDS), we found that bw had a long-lasting impact on steroid metabolism, with significant differences regarding DHEAS metabolites and relative androgen production. However, most parameters showed significant intra-twin correlations, suggesting a consistent interrelationship between prenatal environment, genetic background, and steroid metabolism.

IGF-I in cord blood is predictive of final height in monozygotic twins with intra-twin birth weight differences.

OBJECTIVE: Adverse prenatal conditions can exert a long-lasting impact on growth up to final height (FH). Due to different prenatal nutrient availability, monozygotic twin pairs with discordant birth weight (bw) provide an excellent model to examine the impact of genes and environment and to analyse the predictive value of bw, birth length (bl) and cord blood (cb) concentration of IGF-I on FH. PATIENTS AND METHODS: Twenty eight monozygotic twin pairs with intra-twin bw-/bl-differences were studied at birth and longitudinally until FH. Intra-twin bw difference >1 SDS was defined "discordant" (n = 10 pairs). IGF-I was analysed in cord blood in all twins. Intra-twin differences (∆) in bw, bl and cord blood IGF-I were correlated with ∆FH. RESULTS: Throughout growth and up until FH intra-twin length/height differences remained for all but two (26/28) twins and for all (10/10) discordant twins. In the discordant group, a highly significant intra-twin difference for FH-SDS was found with a mean intra-twin Δheight- SDS of 1.23 (range, 0.29-2.34). This corresponds to a mean Δintra-twin difference at FH of 7.9 cm (3.1 inch; range, 2-15 cm [0.79-5.9 inch]). Correlation coefficients were calculated to identify factors predicting FH: ∆bw (r = .678; P = .0005), ∆bl (r = .333; P = .0002) and ∆IGF-I in cb (r = .418; P = .0023). Interaction terms showed that IGF-I is an additional factor to the auxological data, leading to an improvement of the ∆FH modelling. CONCLUSION: Prenatal environment leading to bw-/bl- and cbIGF-I differences in monozygotic twins had a long-lasting impact on growth until FH. Both, anthropometric data at birth and cbIGF-I are predictive of FH.