The controlled "superovulation" techniques used in IVF are designed to stimulate the ovaries to produce several eggs (oocytes) rather than the usual single egg as in a natural cycle. Multiple eggs increase the potential availability of multiple embryos (fertilized eggs) for transfer and ultimately increase the probability of conception.

 Agonist - (Triptorelin or Leuprolide acetate) is a hormone which when given as a subcutaneous (just below the skin) injection, will stimulate the "turning-off" of the pituitary gland. This suppressive action enables recruitment of multiple follicles and prevents the eggs from being released from the ovary by the body. This enables retrieval of a large number of eggs at a time suitable to the doctor. The injection is taken at the same time everyday.

Antagonist (Cetrorelix or Ganirelix acetate) are newer hormones whose effective action is similar to the Agonist in that they prevent premature ovulation.

FSH is a hormone, normally produced by the pituitary, used to stimulate the ovaries to produce multiple eggs.

HMG is a hormone which is a combination of the hormones FSH and LH that are normally produced by the pituitary. It stimulates the ovaries to produce more eggs. 

HCG is a hormone, similar to the hormone LH that is normally produced by the pituitary. This medication is used to ripen the developing eggs and initiates the release of the eggs from the ovaries.