Autism spectrum disorders (ASD) and iodine deficiency disorders (IDDs) are both global health problems. Autism spectrum disorder has no single known cause . The major challenge facing progress in research into the etiology of autism is the complex interplay between many factors (environmental, genetic, social) and their poorly understood effect on the function and development of the autistic brain. ASD are developmental disorders that become evident during early childhood. Usually they are evidenced by problems forming relationships, difficulty communicating with other people and certain abnormal behavioral patterns. ASD is an umbrella term that was outlined by diagnosis criteria presented in the Diagnostic and Statistical Manual of Mental Disorders (DSM), currently in its 5th edition  and encompasses what were previously recognized as distinct subtypes including autistic disorder, Asperger syndrome, childhood disintegrative disorder and pervasive developmental disorder-not otherwise specified. The exact number of children affected by ASD in Poland is hard to quantify. Up until 2010 the healthcare & disability coding system did not distinguish between persons affected by autism disorders and other psychiatric or neurological problems. However, we do know that the global trend of increasing ASD diagnosis is consistent with the increasing incidence here in Poland  ; . The best estimates indicate that around 30,000–50,000 children in Poland are affected by ASD .
Although the exact etiology of ASD is unknown, the subject is one of much recent inquiry. Numerous studies have documented statistically significant nutritional and metabolic aberrations in persons affected by ASD when compared to normal populations  ; . Abundant effort has been devoted to determining the content of elements that may contribute to the development of ASD, even if their exact mechanism or roles in the disorder remain unclear.
Iodine is a particularly important microelement in human physiology—it plays a crucial role as a component of thyroid hormones and deficiency at any stage of life can cause significant clinical manifestations ; ; ; ;  ; . The most critical time for proper iodine status, however, is early in life—hypothyroidism due to iodine deficiency which can lead to impaired neurodevelopment. Adequate levels of thyroid hormones are especially important for myelination, cell migration, differentiation and maturation of the fetal brain ;  ; . IDD are caused primarily by insufficient dietary iodine intake and/or inadequate iodine utilization due to, for example, the presence of goitrogens  ; .
In one study performed in Egypt, 54% of tested autistic children were found to be iodine deficient . Another study performed in USA found 45% lower iodine content in hair of children with autism when compared with healthy controls . Up until now, such studies have not yet been performed in Poland. There is also a lack of current data assessing the effectiveness of iodine prophylaxis in Polish children between the ages of 2 and 17 years and whether iodine consumption is at a satisfactory level. Although significant steps have been taken in Poland to eliminate iodine deficiency and the resulting disorders , the situation still requires constant monitoring. Measurements of thyroid hormone levels and thyroid stimulating hormone levels are important in the assessment of thyroid function. The majority of dietary iodine, however, ends up in the urine, so although it is not a direct measurement of function, urinary iodine (UI) level is a great indicator of recent iodine intake and low values demonstrate a population is at risk for deficiency ;  ; .
The primary aims of our study were to compare iodine excretion in ASD children with those of their normally developing peers and to correlate iodine status with fifteen common diagnostic criteria for ASD from the Childhood Autism Rating Scale (CARS) in order to check which items on the scale are mostly affected by iodine status. The data were also interpreted to identify whether or not there were any relationships between age, BMI, the severity of individual symptoms of ASD, thyroid hormones and urinary iodine. To the best of our knowledge, studies of iodine status in relation to specific items from the scale measuring the severity of autism are lacking not only in Poland but are also very rare in the entire world.
The severity of certain symptoms in autism is associated with iodine status in maturing boys. Thyroid hormones were within normal reference ranges in both groups while urinary iodine was significantly lower in autistic boys suggesting that further studies into the nonhormonal role of iodine in autism are required.