The joint meeting of the International Endocrine Society (ICE) and the American Endocrine Society (ENDO) (ICE/ENDO2014) was held in Chicago, USA, from June 21 to 24, 2014. Dr. Kenneth B. Ain, Director of the Thyroid Oncology Program at the University of Kentucky, reported the results of a study in which objective cognitive deficits and motor delays in patients with hypothyroidism put their safety in driving vehicles at risk. The study enrolled 32 patients who completed a series of neurocognitive and psychological tests, and the researchers also used a driving simulator to examine the patients’ performance at three time points: when thyroid function was normal, when transient hypothyroidism was present, and when thyroid function was normal after resumption of thyroid hormone therapy. The results showed that when patients were in a hypothyroid state, braking time on the driving simulator was prolonged by 8.5%, which is equivalent to the degree of impaired driving ability observed by other researchers in subjects with blood alcohol concentrations up to 82 mg/dl. In the United States, a blood alcohol concentration of 82 mg/dl falls into the category of illegal driving. Test results during hypothyroidism showed a significant decrease in executive function and information processing speed, and a 13 percent slowing of fine hand movements. “These findings provide us with objective evidence that hypothyroid patients should not drive motor vehicles and should wait until thyroid function returns to normal before lifting driving restrictions.” Dr. Ain consistently warns hypothyroid patients against driving in written medical orders, but most clinicians do not warn their patients about reduced driving ability, and this is not mentioned in the joint guidelines of the American Thyroid Association (ATA) and the American Association of Clinical Endocrinologists (AACE), largely due to the lack of objective quantitative evidence to support such warnings to patients. Not only that, but once a diagnosis of severe hypothyroidism is made and thyroid hormone replacement therapy is prescribed, patients will be delayed for some time before they return to normal thyroid function. Levothyroxine has a half-life of 1 week and takes 6 to 8 weeks to reach a steady state. It often takes at least 2 weeks of treatment to bring about improvement in impaired neurology. “This is really a public health issue and there is a need to make the public aware of this danger.”