the general name for two hormones that stimulate activity and hormone production in the gonads (the ovaries or testicles). These are both secreted by the pituitary gland and are called Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH).
English spelling for gonadotropin. The etymological derivation of the spellings is different, though. A trophic effect of a hormone implies a nourishing action, whereas a tropic effect of a hormone implies a switching action; arguably it's the latter (American) usage that is now known to be the more physiologically correct.