Chimeric peptide epitopes can serve as effective immunogens against hormones and other small peptides or proteins. Thus, immunogenic peptides are selected from promiscuous Th epitopes and synthesized together with self antigenic peptide sequences fused with or without end to end spacer peptide interconnections. A peptide sequence which may be of the gonadotropin releasing hormone is linked with an immunogenic peptide sequence selected from a promiscuous Th-epitope of measles virus protein F, tetanus toxoid, or malaria protein CSP. Compositions of the chimeric immunogen are found effective in eliciting high and specific anti-GnRH antibody titers.