需要对左甲状腺素（LT4）+左甲状腺素（LT3）联合治疗甲状腺功能减退的风险和益处进行证据支持。我们进行了一项随机、双盲、安慰剂对照的研究，评估了LT4 + LT3治疗与LT4 +安慰剂在同质化无心血管风险因素的无甲状腺患者中的效果，其长期接受LT4替代单一疗法。本研究的首要目标是通过心电图和多普勒超声心动图评估LT4 + LT3联合治疗对心率、心律和敏感心血管参数的影响，包括心脏形态和功能。本研究的次要目标是评估患者的依从性、耐受性和潜在不良事件。在300名低风险甲状腺癌随访患者中，根据纳入标准选择了38名术后甲状腺功能减退患者，随机分配接受LT4 + LT3或LT4 +安慰剂治疗，经过一年治疗后评估了24名患者。将所有临床和实验室参数与性别、年龄、体力活动和生活方式匹配的50名健康甲状腺功能正常志愿者的结果进行比较。参与者和临床医生对治疗分配保持盲法。在一年的联合治疗后，与LT4 +安慰剂组相比，LT4 + LT3组的舒张功能显著改善，表现为E/e'比值显著降低（p = 0.046）并呈现积极的时间趋势。此外，单变量分析显示，在LT4 + LT3组中，F-T3水平（pg/ml）与E/e'比值变化 Δ之间存在显著关联关系（标准化β系数 = 0.603（CI 95%: 0.001 - 1.248），p值 = 0.050）。从首次给药到研究结束期间未发生包括心动过速、心律失常、房颤或其他重要事件在内的任何不良事件。在这份初步报告中，LT4 + LT3联合治疗在舒张功能心血管参数上引起了有利的变化，且未出现任何不良心血管事件。EUDRACT编号：2017-001261-25。

Evidence is needed on the risks and benefits of combination therapy with Levothyroxine (LT4) + Liothyronine (LT3) for treatment of hypothyroidism.We performed a randomized double-blind placebo-controlled study to assess the effects of LT4 + LT3 therapy vs LT4 + placebo in a homogenous group of athyreotic patients, without cardiovascular risk factors during long-term replacement monotherapy with LT4. The primary objective of the study was to assess the effects of combination LT4 + LT3 therapy on heart rate, cardiac rhythm and sensitive cardiovascular parameters of cardiac morphology and function by means of electrocardiography and Doppler echocardiography. The secondary objective of the study was to evaluate patient compliance, tolerability, and potential adverse events.Thirty-eight patients with post-surgical hypothyroidism satisfying the inclusion criteria were selected form a group of three hundred patients with low-risk thyroid cancer followed for a routine follow-up; they were randomized to receive LT4 + LT3 or LT4 + placebo. Twenty-four patients were evaluated after one year of treatment. All clinical and laboratory parameters were compared to the results obtained in fifty healthy euthyroid volunteers without comorbidities, matched for gender, age, physical activity and lifestyle. Participants and clinicians remained blinded to the treatment allocation. After one year of combination therapy, a significant improvement in the diastolic function, evidenced by a significant reduction in the E/e' ratio (p =0.046) and its positive trend over time, was observed in the LT4 + LT3 group vs. the LT4 + placebo group. In addition, the univariate analyses showed a significant relationship between F-T3 levels (pg/ml) with Δ of variation of E/e' ratio in LT4 + LT3 group. (Standardized ß coefficient = 0.603 (CI 95%: 0.001 - 1.248), p-value = 0.050) after combination therapy. No adverse events including tachycardia, arrhythmias, atrial fibrillation, or other important events occurred between the first administration and the end of the study.In this preliminary report, combination treatment with LT4 + LT3 induced favorable changes in cardiovascular parameters of diastolic function without any adverse cardiovascular events.EUDRACT n: 2017-001261-25.