Steroidogenic pathway from the cholesterol precursor lanosterol to the sex steroids testosterone and estradiol. Sterols and steroids that have been shown to promote mouse oocyte maturation in vitro are enclosed in a box, whereas steroids known to trigger oocyte maturation in frogs (in addition to testosterone) are enclosed in a circle. FF-MAS, follicular fluid-derived meiosis-activating sterol; CYP, cytochrome P450 enzyme; DHEA, dehydroepiandrosterone; HSD, hydroxysteroid dehydrogenase.