Hypothesis: Impaired Thermoregulation and Glymphatic Clearance in Hashimoto's Thyroiditis as an Etiological Pathway for Morning Migraines

Morning migraines represent a distinct clinical subtype of primary headache characterized by awakening attacks. While Cortical Spreading Depression (CSD) initiated by extracellular glutamate accumulation is the established electrophysiological mechanism of migraine aura and pain activation, the upstream physiological drivers of nocturnal CSD remain incompletely elucidated. This paper presents the Hypothyroid-Glymphatic-Migraine (HGM) Hypothesis, proposing that autoimmune thyroiditis (Hashimoto’s Thyroiditis) disrupts nocturnal glymphatic waste clearance through a triad of pathophysiological mechanisms: Impaired hypothalamic core temperature regulation secondary to low bioavailable triiodothyronine (T3), truncating Stage 3 Non-REM slow-wave sleep; Downregulation and mislocalization of astrocytic Aquaporin-4 (AQP4) water channels driven by systemic thyroid insufficiency and neuroinflammation; and Mechanical drainage impedance at the cervical lymphatics resulting from mucopolysaccharide-induced fluid retention (myxedema). Together, these disruptions prevent the clearance of metabolic waste and glutamate from the visual cortex overnight, creating a hyper-excitable microenvironment primed for morning CSD ignition upon awakening. The hypothesis provides a unified physiological framework linking autoimmune thyroid disease, sleep architecture disruption, glymphatic stagnation, and morning migraine onset, and outlines testable experimental approaches for validation.