甲状腺功能减退患者应当避免驾车

芝加哥——在国际内分泌学会（ISE）与内分泌学会（ES）联合举办的一场会议上，肯塔基大学甲状腺肿瘤项目主任Kenneth B. Ain医生报告了一项纵向研究的结果：甲状腺功能减退患者的客观认识缺陷和运动迟缓使得他们驾驶车辆的安全性堪忧。

这项研究招募了32例甲状腺癌患者，这些患者完成了一系列神经认知和心理测试，研究者还利用驾驶模拟器检测了这些患者在3个时间点的表现：甲状腺功能正常时，在接受抗癌治疗和评估的过程中出现短暂性甲状腺功能减退时，以及恢复甲状腺激素治疗后甲状腺功能正常时。

结果显示，当患者处于甲状腺功能减退状态时，在驾驶模拟器上的刹车时间延长了8.5%，这相当于其他研究者在血液酒精浓度达到82 mg/dl的受试者中观察到的驾驶能力受损程度。在美国，82 mg/dl的血液酒精浓度属于非法驾驶范畴（编者注：在中国亦属于醉酒驾驶）。

在甲状腺功能减退期间的测验结果显示，患者的执行功能和信息处理速度明显下降，手的精细运动减慢了13%。Beck抑郁自评量表平均得分从7.9恶化至18.9，相当于轻度偏中度的抑郁症，特征是有植物神经症状和情绪改变但没有其他类型抑郁症常有的自尊心受损和负罪感。

Kenneth B. Ain医生

“这些发现为我们提供了客观证据，表明甲状腺功能减退患者不宜驾驶机动车辆，应当等到甲状腺功能恢复正常才能解除驾车限制。”Ain医生始终坚持在书面医嘱中警告甲状腺功能减退患者不要开车，但多数临床医生并不会提醒患者注意驾驶能力下降的问题，美国甲状腺学会（ATA）和美国临床内分泌医师协会（AACE）联合指南中也未提及这一点。Ain医生指出，这主要是由于缺乏客观的量化证据支持向患者提出此类警告。

 “等到我们的研究被发表后，涉及严重机动车辆事故的甲状腺功能减退患者将会被视为受害者。假如临床医生不警告患者注意这一风险，就可能将承担一部分责任，这与没有警告癫痫大发作患者避免驾车的神经科医生会被视为过错方是一样的道理。”

Ain医生在接受采访时表示，接受短暂性甲状腺激素耗竭治疗的甲状腺癌患者在所有甲状腺功能减退的驾车人群中只占一小部分。根据Framingham心脏研究的数据，60岁以上人群中有4.4%患有甲状腺功能减退，这些患者中有很多未得到诊断或治疗。并且据估计，左旋甲状腺素治疗的不依从率高达17%~32%。

不仅如此，一旦被诊断为严重甲状腺功能减退并被开具甲状腺激素替代治疗处方，患者将会滞后一段时间才能恢复甲状腺功能正常状态。左旋甲状腺素的半衰期为1周，需要6~8周达到稳定状态。往往需要治疗至少2周才能使神经病学受损有所改善。“这其实是一个公共卫生问题，有必要让公众了解这一危险。”

Ain医生报告称接受了健赞公司提供的研究补助，该公司资助了本项研究。

爱思唯尔版权所有  未经授权请勿转载

 

By: BRUCE JANCIN, Internal Medicine News Digital Network

CHICAGO – Hypothyroid patients exhibit objective cognitive deficits and motor slowing rendering them unsafe to operate a motor vehicle.

That’s the key take-home message from a longitudinal study in which 32 patients with thyroid cancer completed an extensive battery of neurocognitive and psychological tests as well as measured performance on a driving simulator at three time points: while euthyroid, again while temporarily hypothyroid as part of their cancer therapy and assessment, and finally while once again euthyroid after restoration of thyroid hormone therapy.

"These findings provide objective evidence warranting admonitions against operating motor vehicles for hypothyroid patients and confidence in removing such stipulations upon restoration of a euthyroid state," Dr. Kenneth B. Ain said at the joint meeting of the International Society of Endocrinology and the Endocrine Society.

In his own clinical practice he has long included a boxed warning against driving while hypothyroid on all of his written instructions to patients. But most physicians don’t warn their hypothyroid patients that they are driving impaired, nor do the joint practice guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists address the issue. That’s largely because there hasn’t been objective, quantitative evidence to provide firm support for such cautionary admonitions – until now, observed Dr. Ain, professor of medicine and director of the thyroid oncology program at the University of Kentucky, Lexington.

While hypothyroid, study participants experienced an 8.5% increase in braking time on a driving simulator. That’s equivalent to the degree of impairment other investigators have shown to be associated with a blood alcohol level of 82 mg/dL, which is above the legal driving limit in the United States.

"Once our study is published, a patient who is involved in an auto accident [in which] there is death or significant harm could be considered an impaired patient. And if physicians do not warn the patient of this risk, they would be considered an agent of harm. They could be liable for the consequences, the same as a neurologist who doesn’t warn a patient with a grand mal seizure disorder not to drive," Dr. Ain said.

In an interview, he noted that thyroid cancer patients undergoing thyroid hormone depletion temporarily as part of their treatment are merely a small fraction of the total impaired hypothyroid driver population. Investigators with the Framingham Heart Study have reported that 4.4% of individuals above age 60 are hypothyroid. Many of these individuals remain undiagnosed or undertreated. Plus, the noncompliance rate with levothyroxine therapy has been estimated at 17%-32%.

Moreover, once a patient is newly diagnosed as being profoundly hypothyroid and receives a prescription for thyroid hormone replacement, there is a lag time involved in achieving a euthyroid state. The half-life of levothyroxine is 1 week. It takes 6-8 weeks to reach a steady state. Probably at least 2 weeks of therapy are required before there is any improvement in the neurologic impairments documented in this study, Dr. Ain speculated.

"We’re really talking here about a public health problem, one that requires a public health response and acknowledgment that this is a danger," according to the endocrinologist.

Testing during the hypothyroid phase of the study showed significant declines in measures of executive function and information-processing speed. Fine motor performance of the hands was slowed by 13%. Mean scores on the Beck Depression Inventory deteriorated from 7.9 while euthyroid to 18.9 while hypothyroid, consistent with mild bordering on moderate depression; this depression was characterized by vegetative symptoms and altered mood, but without the impaired self-esteem and sense of guilt often characteristic of other forms of depression.

Dr. Ain reported receiving a research grant from Genzyme, which funded this study.