Autism spectrum disorder (ASD), a heterogeneous group of neurodevelopmental disorders, is characterized by social impairment and repetitive and stereotypic behaviors. Because of the lack of approved laboratory diagnostic markers and effective therapeutic medications, it is one of the most challenging diseases. Therefore, it is urgent to explore potential diagnosis markers or therapeutic targets. Insulin-like growth factor 1 (IGF-1) is a neurotrophic growth factor that enhances brain development. IGF-1 levels in body fluids are lower in preschool children with ASD than in typically developing children, which may serve as a potential diagnostic marker. In various ASD models associated with genetic or environmental exposure, IGF-1 treatment can improve core symptoms or pathological changes, including neuronal development, neural cell survival, balance of synaptic excitation and inhibition, neuroimmunology, and oxidative stress status. In March 2023 an IGF-1 derivative was approved as the first drug for treating Rett syndrome, an ASDrelated neurodevelopmental disorder, to improve fundamental symptoms such as social communication. Thus, in this review, we present accumulating evidence of altered IGF-1 levels in ASD patients and the possible mechanisms, as well as evidence that IGF-1 treatment improves the pathophysiology in various ASD models. IGF-1 has the potential to be an early diagnosis marker and an effective therapeutic for ASD.

Recent studies have indicated that there are imbalances in neurotransmitter levels in children with autism spectrum disorder (ASD). Alterations in peripher