Ageing-associated hypothyroidism and acute thyroidectomy increased the transport of liver-derived ApoE4 to exosomes and into the brain, where ApoE4 activated the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome by increasing the cholesterol level in neural cells. The gene discussed is APOE; the disease is hypothyroidism.