[Association of Pathological Progression of Parkinson's Disease and the Thyroid Gland]

Various neurological disturbances in mental status, cognitive function, emotion, and motor function are observed owing to hypo- or hyperthyroidism. Although excretion of thyroid hormones is tightly regulated by the hypothalamus-pituitary gland-thyroid axis, it is partly influenced by blood flow regulated by the postsynaptic sympathetic fibers. In patients with Parkinson's disease in early stages, previous studies using cardiac MIBG scintigraphy or fluorodopa positron emission tomography showed mild-to-moderate denervation of the thyroid. However, whether the autonomic denervation of the thyroid may influence its excretion function, potentially leading to systemic metabolic changes originating from other organs, remains unclear. In this context, we examined the association of thyroid function with Parkinson's disease focusing on the autonomic nervous system referring to our latest achievement. Cardiac MIBG scintigraphy identified decreased uptake of the thyroid especially in early stages of Parkinson's disease with constipation, implying systemic autonomic denervation. Using multiomics analyses, we identified that the autonomic denervation-hypothyroidism-liver axis presented with insufficient fatty acid β-oxidation in patients with de novo Parkinson's disease.