APP and Alzheimer disease: However, data regarding the activity of these enzymes in neurodegenerative diseases is severely limited, with one study reporting increased expression of 3α-HSD3 in the prefrontal cortex of AD patients with both sexes grouped according to Braak stage (Luchetti et al., 2011a), while others have reported increased 5α-reductase expression in 12-month old APP/PS1 double transgenic AD mice (Porcu et al., 2016).