<p>Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental condition characterized by deficits in social communication and restricted, repetitive behaviors. Although traditionally linked to synaptic protein dysfunction and neurotransmitter imbalance, growing evidence suggests that broader intracellular signaling networks critically regulate the neurodevelopmental processes disrupted in ASD. This review synthesizes current evidence on four interconnected signaling pathways—Klotho, GDNF/GFRA-1, IGF-1, and GLP-1—and examines their potential roles in ASD pathophysiology within a unified mechanistic framework. These pathways regulate fundamental processes, including neuronal survival, synaptogenesis, dendritic maturation, myelination, modulation of oxidative stress, neuroinflammation, and metabolic homeostasis. Importantly, they converge on shared intracellular cascades such as PI3K/Akt, MAPK/ERK, mTOR, and Wnt/β-catenin, which are increasingly implicated in ASD-related abnormalities in synaptic plasticity and circuit organization. Experimental models demonstrate that dysregulation of these signaling systems can impair hippocampal function, alter excitatory–inhibitory balance, and disrupt structural connectivity. Among them, IGF-1 has shown promising translational potential in clinical trials for syndromic ASD, while GLP-1 receptor agonists and Klotho modulation represent emerging therapeutic avenues. The GDNF/GFRA-1 axis further highlights the importance of trophic support in maintaining synaptic integrity and neuronal resilience. By integrating molecular, preclinical, and clinical findings, this review proposes that convergent dysregulation of trophic and metabolic signaling pathways may contribute to ASD heterogeneity. A systems-level understanding of these interconnected mechanisms may facilitate biomarker development and support the advancement of stratified, pathway-targeted therapeutic strategies.</p>