ESPE Abstracts

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.