Many marker genes have been identified in the adrenal gland’s inner cortex (Table 2). The two commonly used marker genes for the X-zone are 20αHSD (encoded by Akr1c18) (Hershkovitz, Beuschlein, Klammer, Krup, & Weinstein, 2007) and Pik3c2g (Pihlajoki et al., 2013). Other marker genes that are also expressed in the inner cortex but partially colocalized with 20αHSD include thyroid hormone receptor β1 (TRβ1) (Huang, Kraft, Moy, Ng, & Forrest, 2015), DHCR24 (Zheng et al., 2023), and CYP2F2 (Lyu et