Peptide contraception: antifertility properties of LH-RH analogues.

A prototype LH-RH antagonist dampened the proestrous gonadotropin surge and blocked ovulation but had no effect on pregnant animals. In contrast, LH-RH and two highly potent LH-RH agonists terminated pregnancy when administrated prior to or following implantation. This contragestational effect, as well as other antireproductive properties of the agonists, coupled with the reversibility of their effects, strongly suggest that peptides may provide a new basis for contraception.