TG and Alzheimer disease: In men with PCDS, tyrosine metabolism, a pathway that influences the production of catecholamine and thyroid hormones, is altered, evidenced by increased thyroxine levels and decreased dopamine‐β‐hydroxylase (DBH) levels, a protein primarily expressed in the central nervous system and found to have reduced activity in post‐mortem hippocampus and neocortex samples from Alzheimer's disease patients (Mustapic et al., 2013).