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). This evidence concerns the gene TG and early-onset autosomal dominant Alzheimer disease.