Muscle metabolism and exercise tolerance in subclinical hypothyroidism: A controlled trial of levothyroxine
Muscle metabolism and exercise tolerance in subclinical hypothyroidism: A controlled trial of levothyroxine
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DOI：
10.1210/jc.2004-2344
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发表时间：
2005-07-01
影响因子：
5.8
通讯作者：
Ferrannini, E
中科院分区：
文献类型：
--
作者：
Caraccio, N;Natali, A;Ferrannini, E
背景：亚临床甲状腺功能减退症(ShT)已有神经肌肉症状和肌肉能量代谢受损的描述。目的：本研究的目的是采用标准化方案评估SHT患者的能量和底物反应，并以双盲、随机、安慰剂对照的方式检验L-T-4替代治疗的效果。在递增负荷运动中测量摄氧量(VO2)、二氧化碳排出量和心率。测定安静时、运动中每隔2分钟和恢复20分钟时的血糖、乳酸、丙酮酸、游离脂肪酸、甘油和β-羟丁酸浓度。结果：SHT患者的最大功率输出(P=0.02)和最大摄氧量(P=0.04)均降低，随着工作负荷的增加，患者在相当于对照组的VO2值时心率增加(P<；0.03)。呼吸商增量明显高于对照组(P<；0.04)。患者的血乳酸和丙酮酸及其比值升高的斜率比对照组更大(P<；0.0001，P<；0.001和P<；0.01)。在基线、运动和康复期间，患者的静息血浆游离脂肪酸和血甘油水平显著高于对照组(分别为P<；0.0003和P<；0.003)。L-T-4替代物在改善神经肌肉症状的同时，对运动的能量或底物的反应没有产生明显的变化。结论：SHT患者的运动反应在耐受性和底物利用模式方面都发生了改变。恢复稳定的甲状腺功能正常并不能在一年内纠正这种缺陷。
Background: Neuromuscular symptoms and impaired muscle energy metabolism have been described in subclinical hypothyroidism (sHT).Aim: The aim of the study was to evaluate the energy and substrate response to exercise in sHT patients using a standardized protocol and to test the effect of L-T-4 replacement in a double-blind, randomized, placebo-controlled fashion.Patients and Methods: We studied 23 sHT patients and 10 matched euthyroid controls. Oxygen uptake (VO2), carbon dioxide output, and heart rate were measured during incremental step-up exercise. Blood glucose, lactate, pyruvate, free fatty acid, glycerol, and beta-hydroxybutyrate concentrations were measured at rest, every 2 min during exercise, and during 20 min of recovery. The exercise protocol was repeated after 6 months of placebo or L-T-4-restored euthyroidism.Results: Maximal power output ( P = 0.02) and VO2 max ( P = 0.04) were reduced in sHT, and, with increasing workload, patients achieved higher heart rates ( P < 0.03) at VO2 values equivalent to those of controls. The respiratory quotient increments were significantly higher in patients than controls ( P < 0.04). Blood lactate and pyruvate and their ratio rose with a steeper slope ( P < 0.0001, P < 0.001, and P < 0.01, respectively) in patients than controls. Resting plasma free fatty acid and blood glycerol levels were significantly higher in patients than controls ( P < 0.0003 and P < 0.003, respectively) throughout baseline, exercise, and recovery. L-T-4 replacement, while improving neuromuscular symptoms, did not produce significant changes in the energy or substrate response to exercise.Conclusions: The response to exercise is altered both in terms of tolerance and pattern of substrate utilization in sHT patients. Restoring stable euthyroidism does not correct this defect over a 1-yr period.