The Thyroid-Brain Network: Exploring Inflammation, Immune Mechanisms, and Common Triggers in Thyroid-Related Neurological Dysfunction.

Abstract

Background: Autoimmune thyroid diseases (AITD), encompassing Hashimoto's thyroiditis and Graves' disease, constitute the most prevalent endocrine disorders globally, affecting hundreds of millions of individuals. Despite their high prevalence, the neurological consequences of AITD remain substantially under-recognized in clinical practice. Historically, thyroid dysfunction has been viewed primarily within an endocrine premise, with neurological manifestations attributed solely to altered thyroid hormone levels. However, emerging evidence establishes inflammation and immunity as critical mediating links connecting peripheral thyroid dysfunction to central nervous system manifestations. This review engages current understanding of the mechanistic pathways through which AITD impacts brain function, emphasizing shared pathogenic origins and potential therapeutic implications.

Summary: Thyroid hormones function as essential neuromodulators governing neurodevelopment, synaptic plasticity, and cognitive processing through both genomic and non-genomic mechanisms. The immunological perspective reveals that AITD propagates neuroinflammation via convergent pathways: molecular mimicry between thyroid and neural antigens, cytokine-mediated disruption of neurotransmitter metabolism, HMGB1-driven glial activation, and blood-brain barrier compromise facilitating immune cell infiltration. The thyroid-gut-microbiota axis emerges as a critical mediator wherein dysbiosis perpetuates both thyroid autoimmunity and neuroinflammation through impaired serotonin precursor availability and increased intestinal permeability. Mitochondrial dysfunction represents an energetic common denominator as thyroid hormone dysregulation impairs oxidative phosphorylation, producing region-specific cerebral metabolic disturbances. Simultaneous compromise of monoamine systems, cholinergic signaling abnormalities, and glutamate excitotoxicity creates a particularly toxic neurochemical state. Common triggers such as psychological stress, gut dysbiosis, and mitochondrial impairment may activate interconnected pathways that simultaneously compromise thyroid and brain function, revealing shared mechanistic origins.

Key messages: Neurological consequences of AITD are prevalent but under-recognized. Inflammation and immunity serve as the mechanistic bridge. The thyroid-gut-microbiota axis is a critical therapeutic target. Mitochondrial dysfunction is the energetic common denominator. Untreated thyroid dysfunction creates a uniquely toxic neurochemical state. Shared triggers reveal fundamental mechanistic unity.