Background: Low birth weight (bw) and unfavourable intrauterine conditions are associated with a subsequent impact on the endocrine system. However, very little is known about the impact on thyroid function.
Objective and hypotheses: In a longitudinal study we observed genetically identical twins with intra-twin bw-differences from birth until adolescence to objectify the impact of a lower bw on development and health in later life.
Method: Bw-difference of <1SDS was defined concordant, bw-difference >1SDS discordant. Blood sampling was performed at a mean age of 9.8 yrs (12 concordant, 13 discordant) and 14.6 yrs (14 concordant, 11 discordant).
Results: At 9.8 yrs, no significant differences in TSH, T3, T4 and TBG levels were represented in the concordant twins. However, in the discordant group, a significant difference in TSH levels was found (P=0.016). The former smaller twins had higher TSH mean concentrations than their former larger co-twins (3.76 vs 2.46 μU/ml). No significant differences were observed in T3, T4 and TBG levels. At 14.6 yrs, again, we did not observe any significant differences in TSH, T3, fT4, T4 and TBG levels in the concordant group, whereas the discordant group showed a significant difference in TSH concentration (P=0.016). Once more, the former smaller twins revealed higher TSH mean levels than their former larger co-twins (2.86 vs 2.22 μU/ml) and no significant differences were observed in T3, fT4, T4 and TBG levels. In all twin-pairs, at 14.6 yrs, the former smaller twins still had a significant lower BMI-SDS than their larger co-twins (P < 0.001).
Conclusion: In this special group of monozygotic twins with intra-twin bw-differences, we could show that bw has a long-lasting impact on thyroid function. The significantly higher TSH concentrations at 9.8 and 14.6 yrs in the former smaller twins who were born with a greater bw-difference indicate the possibility of a TSH-set-point-alteration in low-bw-children.
10 - 12 Sep 2016
European Society for Paediatric Endocrinology