Ng Sze May, Turner Mark A, Gamble Carrol, Didi Mohammed, Victor Suresh, Atkinson Jessica, Sluming Vanessa, Parkes Laura M, Tietze Anna, Abernethy Laurence J, Weindling Alan Michael
Department of Women's and Children's Health, Institute of Translational Medicine, University of Liverpool, Crown Street, L8 7SS, Liverpool, UK,
Pediatr Radiol. 2014 Aug;44(8):987-96. doi: 10.1007/s00247-014-2911-6. Epub 2014 Mar 27.
In order to assess relationships between thyroid hormone status and findings on brain MRI, a subset of babies was recruited to a multi-centre randomised, placebo-controlled trial of levothyroxine (LT4) supplementation for babies born before 28 weeks' gestation (known as the TIPIT study, for Thyroxine supplementation In Preterm InfanTs). These infants were imaged at term-equivalence.
Forty-five TIPIT participants had brain MRI using diffusion tensor imaging (DTI) to estimate white matter development by apparent diffusion coefficient (ADC), fractional anisotropy (FA) and tractography metrics of number and length of streamlines. We made comparisons between babies with the lowest and highest plasma FT4 concentrations during the initial 4 weeks after birth.
There were no differences in DTI metrics between babies who had received LT4 supplementation and those who had received a placebo. Among recipients of a placebo, babies in the lowest quartile of plasma-free thyroxine (FT4) concentrations had significantly higher apparent diffusion coefficient measurements in the posterior corpus callosum and streamlines that were shorter and less numerous in the right internal capsule. Among LT4-supplemented babies, those who had plasma FT4 concentrations in the highest quartile had significantly lower apparent diffusion coefficient values in the left occipital lobe, higher fractional anisotropy in the anterior corpus callosum and longer and more numerous streamlines in the anterior corpus callosum.
DTI variables were not associated with allocation of placebo or thyroid supplementation. Markers of poorly organised brain microstructure were associated with low plasma FT4 concentrations after birth. The findings suggest that plasma FT4 concentrations affect brain development in very immature infants and that the effect of LT4 supplementation for immature babies with low FT4 plasma concentrations warrants further study.
为了评估甲状腺激素状态与脑部磁共振成像（MRI）结果之间的关系，一部分婴儿被纳入一项多中心随机、安慰剂对照试验，该试验旨在研究对妊娠28周前出生的婴儿补充左甲状腺素（LT4）（即“早产儿甲状腺素补充研究”，简称TIPIT研究）。这些婴儿在足月时接受了成像检查。
45名TIPIT研究参与者接受了脑部MRI检查，使用扩散张量成像（DTI）通过表观扩散系数（ADC）、分数各向异性（FA）以及流线数量和长度的纤维束成像指标来评估白质发育情况。我们比较了出生后最初4周内血浆游离甲状腺素（FT4）浓度最低和最高的婴儿。
接受LT4补充治疗的婴儿与接受安慰剂治疗的婴儿在DTI指标上没有差异。在接受安慰剂的婴儿中，血浆游离甲状腺素（FT4）浓度处于最低四分位数的婴儿，其胼胝体后部的表观扩散系数测量值显著更高，右侧内囊的流线更短且数量更少。在接受LT4补充治疗的婴儿中，血浆FT4浓度处于最高四分位数的婴儿，其左侧枕叶的表观扩散系数值显著更低，胼胝体前部的分数各向异性更高，胼胝体前部的流线更长且数量更多。
DTI变量与安慰剂或甲状腺补充剂的分配无关。出生后血浆FT4浓度低与脑微结构组织不良的标志物有关。研究结果表明，血浆FT4浓度会影响极不成熟婴儿的脑发育，对于血浆FT4浓度低的不成熟婴儿补充LT4的效果值得进一步研究。
