Behavior and circadian glucocorticoids in prepubertal monozygotic twins with birthweight differences: A prospective longitudinal cohort study on twin-to-twin transfusion syndrome patients.

BACKGROUND/OBJECTIVE: Low birthweight may have adverse sequelae in later life. Therefore, we analyzed behavioral difficulties and salivary glucocorticoid profiles in monozygotic twins with intra-twin birthweight differences due to twin-to-twin transfusion syndrome (TTTS). METHODS: 46 monozygotic TTTS twin pairs with birthweight differences of <1SDS (concordant; n=29) and ≥1SDS (discordant; n=17) were recruited at a mean age of 6.9 years for a prospective longitudinal cohort study. For glucocorticoid analysis, saliva samples were collected (at 7 h, 13 h, 18 h and 21 h) and analyzed with liquid chromatography-tandem mass spectrometry. Parents completed the Strengths and Difficulties Questionnaire. RESULTS: From the parents' perspective, the formerly smaller twins had statistically higher scores regarding hyperactivity (mean 4.63 vs 3.48, p=0.003) and emotional problems (mean 2.67 vs 2.02, p=0.042). Less catch-up growth (Δintra-twin height SDS 4 years of age - Δintra-twin birth length SDS) of the smaller twins was associated with higher scores for hyperactivity (Adj. R²=0.261, p<0.001, ß=-1.88, F(1.44)=16.86, n=46, f²=0.35), while smaller birthweight (Adj. R²=0.135, p=0.007, ß=-0,87, F(1.44)=8.03, n=46, f²=0.16) and birth length (Adj. R²=0.085, p=0.028, ß=-0,78, F(1.44)=5.19, n=46, f²=0.09) were associated with higher scores for peer problems. Greater Δintra-twin for cortisol (7 h: rho=0.337, p=0.029; cumulative: rho=0.458; p=0.024) and cortisone (7 h: rho=0.329, p=0.029; 13 h: rho=0.436, p=0.005) correlated with a greater Δintra-twin for conduct problems. In the discordant group, circa 1 SDS in head circumference persisted from birth (mean SDS: smaller twin -1.18, larger twin -0.08, p<0.001) to present (mean SDS: smaller twin -1.16, larger twin -0.14, p<0.001). CONCLUSION: Higher cortisol and cortisone concentrations in smaller twins were associated with higher scores for conduct problems. Lower birthweight and absent catch-up growth affected the parents' perspective on the smaller twins' behavior. They saw those children as more hyperactive, with more peer problems and emotional problems. Thus, it seems important to introduce regular check-ups where behavioral difficulties can be assessed, and assistance and advice can be given to the families. Due to the persisting smaller head circumference in the smaller discordant twins, this should be measured regularly.

Salivary Diurnal Glucocorticoid Profiles in Monozygotic Twins With Intratwin Birthweight Differences.

CONTEXT: Low birthweight (bw) and unfavorable intrauterine conditions have been associated with metabolic sequelae in later life, but little is known about their impact on glucocorticoid metabolism. OBJECTIVE: We studied monozygotic twins with intratwin bw differences to analyze the long-term impact of bw on glucocorticoid metabolism. METHODS: 46 monozygotic twin pairs with bw differences of <1 SDS (concordant; n = 29) and ≥1 SDS (discordant; n = 17) were recruited. At 6.9 years (mean age), saliva samples were collected (at 7 hours, 13 hours, 18 hours and 21 hour) and analyzed with liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS: We found significant or highly significant intratwin correlations in all twin pairs at 3 of 4 (cortisol), and 4 of 4 (cortisone) time points. Graphic evaluation of the diurnal cortisol patterns for each twin pair showed a distinct alignment in all groups. Analyses of the change of intratwin differences over the day by mixed linear modeling showed no intratwin differences in diurnal patterns. Regression analyses of intratwin differences at 7:00 hours showed a significant influence of catch-up growth, indicating lower cortisol concentrations in smaller twins with more catch-up growth (adj. R2 = 0.159, P = .014, ß = -3.71, F(1,42) = 9.15, f2 = 0.19). CONCLUSION: In monozygotic twins with intratwin bw differences, intratwin catch-up growth showed a moderate influence on intratwin differences in morning cortisol concentrations. We observed no differences regarding diurnal patterns. In contrast, in all groups, we found significant intratwin correlations for cortisol and cortisone over the day and a pronounced graphic alignment of cortisol diurnal patterns. We therefore suggest a predominant significance of the genetic background compared with bw differences on cortisol metabolism.