Monzani F, Di Bello V, Caraccio N, Bertini A, Giorgi D, Giusti C, Ferrannini E
Department of Internal Medicine, University of Pisa School of Medicine, 56126 Pisa, Italy.
J Clin Endocrinol Metab. 2001 Mar;86(3):1110-5. doi: 10.1210/jcem.86.3.7291.
Subclinical hypothyroidism (sHT) affects 5-15% of the general population; however, the need of lifelong L-T(4) therapy is still controversial. As myocardium is a main target of thyroid hormone action, we investigated whether sHT induces cardiovascular alterations. Twenty sHT patients were randomly assigned to receive placebo or L-T(4) therapy and were followed for 1 yr. Twenty sex- and age-matched normal subjects served as controls. Doppler echocardiography and videodensitometric analysis were performed in all subjects. Myocardium textural parameters were obtained as mean gray levels, which were then used to calculate the cyclic variation index (CVI; percent systolic/diastolic change in mean gray levels). Patients had a significantly higher isovolumic relaxation time (3.1 +/- 0.5 vs. 2.6 +/- 0.6; P < 0.03), peak A (0.77 +/- 0.16 vs. 0.56 +/- 0.13 m/s; P < 0.01), and preejection/ejection time (PEP/ET) ratio (0.72 +/- 0.05 vs. 0.57 +/- 0.06; P < 0.03) and a lower CVI (P < 0.0001) than controls. CVI was inversely related to TSH level (P < 0.0001) and PEP/ET ratio (P < 0.01). L-T(4)-treated patients showed a significant reduction of the PEP/ET ratio (P < 0.05), peak A (P < 0.05), and isovolumic relaxation time (P < 0.05) along with a normalization of CVI. Conversely, no changes were observed in the placebo-treated group. In conclusion, sHT affects both myocardial structure and contractility. These alterations may be reversed by L-T(4) therapy.
亚临床甲状腺功能减退症（sHT）在普通人群中的发病率为5% - 15%；然而，终身左甲状腺素（L-T4）治疗的必要性仍存在争议。由于心肌是甲状腺激素作用的主要靶器官，我们研究了sHT是否会引起心血管改变。将20例sHT患者随机分为两组，分别接受安慰剂或L-T4治疗，并随访1年。选取20例年龄和性别匹配的正常受试者作为对照。对所有受试者进行多普勒超声心动图和视频密度分析。通过平均灰度值获取心肌纹理参数，然后用其计算周期性变化指数（CVI；平均灰度值收缩期/舒张期变化百分比）。患者的等容舒张时间显著延长（3.1±0.5对2.6±0.6；P < 0.03），A峰峰值显著升高（0.77±0.16对0.56±0.13 m/s；P < 0.01），射血前期/射血时间（PEP/ET）比值显著升高（0.72±0.05对0.57±0.06；P < 0.03），CVI显著降低（P < 0.0001）。CVI与促甲状腺激素（TSH）水平呈负相关（P < 0.0001），与PEP/ET比值呈负相关（P < 0.01）。接受L-T4治疗的患者PEP/ET比值（P < 0.05）、A峰峰值（P < 0.05）和等容舒张时间（P < 0.05）显著降低，CVI恢复正常。相反，安慰剂治疗组未观察到变化。总之，sHT会影响心肌结构和收缩性。L-T4治疗可能会逆转这些改变。
