Department of Clinical Medicine, University Federico II, 80131 Naples, Italy.
Eur J Endocrinol. 2010 Feb;162(2):289-94. doi: 10.1530/EJE-09-0674. Epub 2009 Nov 10.
Patients with congenital hypothyroidism (CH) display subclinical abnormalities of the cardiovascular system that are related to unphysiological fluctuations of TSH levels and occur despite careful replacement therapy.
The aim of the present case-control study was to evaluate the effects of long-term levothyroxine (l-T(4)) replacement therapy on the vascular district in CH patients by assessing endothelial function with flow-mediated dilation (FMD) and brachial artery distensibility with the measurement of the coefficient of distensibility (DC).
Thirty-two young adults with CH aged 18.9+/-0.2 years and 32 age- and sex-matched controls underwent brachial Doppler ultrasound examination to measure FMD and DC at the time of the study. Hypothyroidism was diagnosed by neonatal screening, and l-T(4) treatment was initiated within the first month of life.
Compared to healthy controls, CH patients had significantly reduced brachial artery reactivity with lower FMD values (8.9+/-5.7 vs 14.1+/-5.1% P=0.003) and decreased vascular distensibility (24.6+/-1.6 vs 27.3+/-3 kPa(-1)x10(-3), P<0.0002). Linear regression analysis revealed that both total and pubertal mean TSH and number of episodes of undertreatment were independent determinants of FMD and DC. Pubertal mean TSH was the best predictor of both FMD and DC (r=0.81 and r=0.87 respectively, P<0.001).
Young adults with CH treated with long-term l-T(4) replacement therapy may have significant impairment of both FMD and DC. Our data suggest that high TSH levels, inadequately corrected by l-T(4) replacement therapy in CH patients especially during puberty, can exert significant effects on the elastic and functional vessel properties.
患有先天性甲状腺功能减退症（CH）的患者表现出心血管系统的亚临床异常，这些异常与 TSH 水平的非生理性波动有关，尽管进行了仔细的替代治疗仍会发生。
本病例对照研究的目的是通过评估血流介导的扩张（FMD）来评估长期左甲状腺素（l-T4）替代治疗对 CH 患者血管区的影响，并通过测量可扩张性系数（DC）来评估肱动脉可扩张性。
32 名年龄为 18.9+/-0.2 岁的年轻 CH 成年患者和 32 名年龄和性别匹配的对照者在研究时接受了肱动脉多普勒超声检查，以测量 FMD 和 DC。通过新生儿筛查诊断为甲状腺功能减退症，在生命的第一个月内开始 l-T4 治疗。
与健康对照组相比，CH 患者的肱动脉反应性明显降低，FMD 值较低（8.9+/-5.7%对 14.1+/-5.1%，P=0.003），血管可扩张性降低（24.6+/-1.6%对 27.3+/-3 kPa(-1)x10(-3)，P<0.0002）。线性回归分析显示，总 TSH 和青春期平均 TSH 以及治疗不足发作次数均为 FMD 和 DC 的独立决定因素。青春期平均 TSH 是 FMD 和 DC 的最佳预测指标（r=0.81 和 r=0.87，P<0.001）。
长期接受 l-T4 替代治疗的 CH 年轻成年患者可能存在 FMD 和 DC 的显著损害。我们的数据表明，高 TSH 水平，尤其是在青春期期间，通过 l-T4 替代治疗不能充分纠正，可对血管的弹性和功能特性产生显著影响。
