How many women have their thyroid checked during pregnancy? And how many do it every trimester, rather than just at the beginning? A recently published Israeli study shows a link between the thyroid and autism: to be precise, it demonstrates that monitoring maternal thyroid hormones for the entire nine months can make the difference between normal neurodevelopment and a nearly tripled risk of autism.
Well-treated chronic hypothyroidism does not increase the risk of autism in children. But persistent hormonal imbalance does, and in a dose-dependent manner: The more trimesters pass without correction, the greater the risk. The fetal brain depends on maternal hormones to develop properly, and if these are lacking during critical stages, the consequences can last a lifetime.
Thyroid and autism: a study that changes perspectives
The team led by Idan Menashe of Ben-Gurion University of the Negev followed 51.296 births between 2011 and 2017 at Soroka University Medical Center in Israel. The data, published in November 2025 on The Journal of Clinical Endocrinology & Metabolism, show that 8,6% of mothers had thyroid dysfunction. Of these, 1.161 had chronic hypothyroidism, 1.600 had gestational hypothyroidism, and 1.054 had both conditions.
The follow-up lasted until January 2021, with a diagnosis of autism spectrum disorder performed at a median age of 4,6 years according to DSM-5 criteria. Result: Chronic hypothyroidism alone, if treated appropriately, did not carry any increased riskBut the combination of chronic and gestational hypothyroidism led to a higher risk.
It's a bit like leaving an engine without oil for months: sooner or later something breaks.
The dose-response pattern: more quarters, more risk
The most significant finding, as mentioned, concerns the cumulative effect. The quarter-by-quarter analysis showed a clear dose-response pattern: hypothyroidism in a single quarter led to a hazard ratio of 1,69. Two quarters: 2,39. Three quarters: 3,25. The longer the hormonal imbalance lasts, the higher the risk.
Maternal thyroid hormones are essential for fetal neuronal migration, especially during the second and third trimesters. When they're lacking, neurons don't reach the right areas of the brain, synapses form atypically, and the risk of impaired neurological development increases. This isn't theory: it's physiology documented by decades of research.
“We discovered that Adequately treated chronic hypothyroidism was not associated with an increased risk of autism in offspring, but persistent hormonal imbalance across multiple trimesters does,” explains Menashe.
“These findings emphasize the need for routine monitoring and timely adjustment of therapy to maintain normal thyroid hormone levels throughout pregnancy.”
Prevention is possible, screening is necessary
The good news is that there is a solution and it is simple: regular checks of thyroid function during all three trimesters. Not only at the beginning, when many women take their first exam. The problem is that Too often screening stops there, and imbalances that emerge in the following months go unnoticed.
The cost of a thyroid hormone test is negligible compared to the social and economic cost of autism. Yet, In many Italian obstetric-gynecological protocols, thyroid monitoring is not standard practice every trimester.
What happens when hormones are missing
They control neuronal migration, synapse formation, and the myelination of nerve fibers. When they are deficient, neurons don't reach where they should. The brain areas responsible for social communication, language, and behavioral regulation develop atypically.
A 2013 Dutch study had already documented that mothers with severe T4 deficiency during the first trimester were 3,89 times more likely to have autistic children. The Israeli research confirms and expands these findings, demonstrating that the risk increases with the duration of exposure to the hormonal imbalance.
Study sheet:
Entity: Ben-Gurion University of the Negev, Soroka University Medical Center
Year: 2025
DOI: 10.1210/clinem/dgaf596
Sample: 51.296 births (2011-2017)
TRL: Level 7 (demonstration in operational environment)
Thyroid and autism, the question that remains
If three blood tests in nine months are enough to drastically reduce the risk of autism related to maternal thyroid, why don't we do them?
The answer isn't technical, it's organizational. National pregnancy surveillance protocols need to include quarterly thyroid screening as a standard. General practitioners and gynecologists need to be trained to recognize the signs of subclinical hypothyroidism. And women need to know that checking their thyroid during pregnancy is not optional.
The link between maternal thyroid and autism is no longer a hypothesis. It's a fact. As long as we continue to treat it as a scientific curiosity rather than a clinical indication, we will continue to miss opportunities for prevention.
And children will continue to pay the price of a hormonal imbalance that could have been corrected with a few euros in tests.
