Prolonged use of synthetic glucocorticoids is, however, associated with adverse metabolic effects including obesity, insulin resistance, and non-alcoholic fatty liver disease (NAFLD) (Woods et al. 2015), and decreased AKR1D1 expression has recently been shown in patients with type 2 diabetes and NAFLD (Valanejad et al. 2018, Nikolaou et al. 2019b). Here, AKR1D1 is linked to obesity due to melanocortin 4 receptor deficiency.