As the number of toddlers around the world diagnosed with autism spectrum disorder (ASD) has surged, many false claims have emerged about what causes the neurological and developmental disorder that affects how they communicate, learn, interact with others, and behave.
Among the disproven theories are that vaccines, emotional trauma, poor parenting, food additives and dyes, sugar, genetically modified organisms, infant formula, Wi-Fi and other electromagnetic fields, and acetaminophen (Tylenol) cause autism.
Existing research suggests that autism is triggered by a blend of very early brain wiring differences, genetic factors, and developmental changes in the fetus. But now, researchers at Ben-Gurion University of the Negev (BGU) in Beersheba believe they have found another factor: Women with a persistent imbalance of thyroid hormone during pregnancy may be at an increased risk of having children with autism.
Research from Negev Autism Center
A team headed by Prof. Idan Menashe in the department of epidemiology, biostatistics, and community health sciences has just published its findings in the Journal of Clinical Endocrinology and Metabolism under the title “Maternal thyroid hormone imbalance and risk of autism spectrum disorder.” The results of the present study indicate that ASD risk increases in direct relation to the severity and duration of thyroid hormone imbalance during pregnancy.
Such hormones produced by the butterfly-shaped endocrine gland located in the front of the neck are vital for fetal neurodevelopment. Gestational thyroid imbalance has been associated with atypical neurodevelopment, including increased risk of ASD.
“We found that while adequately treated chronic thyroid dysfunction was not linked to increased autism risk in offspring, ongoing imbalance across multiple trimesters was,” stated Menashe, who, with his colleagues, established the Negev Autism Center a decade ago. “These findings underscore the need for routine monitoring and timely adjustment of therapy to maintain normal thyroid hormone levels throughout pregnancy,” he told The Jerusalem Post.
“Thyroid function is routinely checked with blood tests during pregnancy. But if hormone levels are not balanced, it takes time to do this, and sometimes the treatment is not successful. The cause of thyroid imbalance in pregnant women is not certain; some have thought it’s due to autoimmunity,” said the autism researcher. “We found that the earlier the problem starts and the longer it persists, the higher the risk of ASD.”
In 2018, the Ministry of Science and Technology provided funding for the facility to become the National Autism Center of Israel. This allowed them to increase their data collection by collaborating with other autism centers in Israel while strengthening the clinical and scientific partnership that we have formed at the center. Three years later, the center received a generous donation from the Azrieli foundation, allowing to further expand research and data collection and to turn Israel into an international leader in ASD research.
The center does not include facilities to treat toddlers with ASD who live in the Negev, as it is devoted to research only. There is a serious shortage of such facilities in the region, as in the periphery everywhere. “It is due to the lack of suitable manpower, and not only the lack of funds,” Menashe added.
The team included BGU’s Leena Elbedour, May Weinberg of the Meir Medical Center in Kfar Saba and Tel Aviv University, and Gal Meiri and Dr. Analya Michaelovski of Soroka-University Medical Center. They followed more than 51,000 births by women who were members of Clalit Healthcare Services (the largest of the four public health funds).
They discovered that mothers with persistent thyroid hormone imbalance across pregnancy were at an increased risk of having babies who were later diagnosed with ASD. They also saw a dose-response pattern in which the longer the time of thyroid dysfunction across trimesters, the higher the risk.
A total of 4,409 (8.6%) of the mothers showed abnormal thyroid function. Of these, 1,161 had chronic hypothyroidism, 1,600 had gestational hypothyroidism (an underactive thyroid during pregnancy), and 1,054 had both chronic and gestational hypothyroidism; in addition, 100 women had chronic hyperthyroidism (an overactive thyroid), 376 had gestational hyperthyroidism, and 15 women had both conditions. Notably, 103 women had indications of both hypothyroidism and hyperthyroidism across different time points. The median age at ASD diagnosis was 4.6 years.
When chronic hypothyroidism was treated during pregnancy, there was not a higher outcome of ASD in the toddlers. But when left untreated for a longer period of time, the risk increased. “These findings underscore the importance of routine thyroid function screening and timely treatment throughout pregnancy,” Menashe declared.
“The prenatal period is a critical window for fetal brain development, and perturbations in neurodevelopmental pathways during this time have been linked to increased ASD risk,” he said. “Multiple maternal exposures have been associated with elevated offspring risk… Disruptions in maternal thyroid hormone levels during pregnancy have been associated with adverse developmental outcomes in offspring, including lower IQ scores and delays in expressive language and nonverbal cognition. However, results of previous research have been inconsistent.” Many women of reproductive age have abnormal thyroid function, and treating it is easy.
Given the prevalence of thyroid dysfunction in women of reproductive age and the availability of accessible treatment for both hypothyroidism and hyperthyroidism, clarifying the relationship between these conditions and ASD is of clinical significance, Menashe said.
The Negev population has a unique ethnic composition in that more than a quarter of its inhabitants are Bedouins, who are responsible for more than half of the births at Soroka. Among women with normal thyroid function, 43.3% were Jewish, compared to 49.6% in the thyroid dysfunction group, but ethnicity did not significantly modify the link between thyroid dysfunction and ASD in the groups the team studied.
The thyroid researcher concluded that, while it’s premature to be sure of the cause of ASD, these results are consistent with recommendations for routine monitoring of thyroid hormone levels and treatment of imbalanced thyroid function with medications to maintain normal thyroid function in pregnancy.