CYP19A1 and hyperandrogenism: An important endogenous hormone, melatonin, is present in the body; long-term exposure to dark environments significantly reduces the granulosa cell surface expression of the melatonin receptor (Mtnr1a), and this decreases the ability of melatonin in regulating glucose metabolism, and also inhibits the expression of the androgen receptor (AR) and CYP19A1, thus reducing the output of aromatase in granulosa cells, hyperandrogenism can occur [148,149].