The invention is based on the discovery that INSP100 is a splice variant of human chorionic somatomammotropin hormone 2 (HCS-B; Q14407) and that INSP104 is a splice variant of human chorionic somatomammotropin hormone 1 (hCS-A;P01243). The invention relates to the use of these proteins and nucleic acid sequences from the encoding genes in the diagnosis, prevention, and treatment of disease. This invention relates to novel proteins, termed INSP100 and INSP104, herein identified as novel splice variants of human Chorionic somatomammotropin hormone 2 (hCS-B; Q14407) and human Chorionic somatomammotropin hormone 1 (hCS-A; P01243) respectively and to the use of these proteins and nucleic acid sequences from the encoding genes in the diagnosis, prevention and treatment of disease. The variants have an altered A-B loop and are therefore predicted to possess altered receptor binding properties. All publications, patents and patent applications cited herein are incorporated in full by reference.