TG and neurodegenerative disease: Although there are still many controversies regarding the relationship between thyroid function and neurodegenerative disease (Villanueva et al., 2013), study showed that the free T3 level was significantly lower in PD patients especially with akinetic-rigid motor subtype, while TSH level was lower in patients with tremor-dominant type or mixed type, suggesting a relation of the thyroid hormone level with PD motor symptoms (Umehara et al., 2015).