**2.5.4 Hair**

Levine et al. (Levine et al., 2007) presented a study on determining iodine concentration in tiny (less than 25 mg) human hair samples. Iodine concentrations from the blinded hair autism study samples ranged from 0.483 to 15.9 µg/g. In Adams' et al. studies (Adams et al., 2006) the mean concentration of iodine in the hair of autistic children has been reported to be lower than in the hair from the control group children. The low level of iodine in the hair of children with autism suggests that iodine could be important in the aetiology of autism, presumably due to its effect on thyroid function.
