CD38 and Infertility: The cell surface enzyme CD38 is well studied for its role as an NAD+ glycohydrolase (Fig. 1B) in inflammation, infertility, senescence, and ageing (1, 2, 3, 38, 39, 40), and there is strong interest in the use of small molecule CD38 inhibitors as a strategy to preserve NAD+ levels (2, 39, 40).