Model of sex steroid production in ovaries. Cholesterol transport within ovarian cells is modulated by the feedback of E2 and T on LH production in the brain and pituitary. These effects are summarized by the Signal Modulation compartment of the model. When LH binds its receptor, it activates G protein recycling and the activation of adenylate cyclase. This produces the necessary cAMP for PKA and phosphodiesterase activation. The signaling cascade ends at the activation of StAR which allows for the translocation of cholesterol into the mitochondria. Once in the mitochondria, cholesterol goes through a series of enzyme-mediated reactions to produce sex steroids.