1. A hybrid protein comprising two coexpressed amino acid sequences forming a dimer, each comprising: a) at least one amino acid sequence selected from the group consisting of a homomeric receptor or a fragment thereof, a chain of a heteromeric receptor or a fragment thereof, a ligand, other than a gonadotropin hormone or a fragment thereof, antibody light or heavy chain, the antibody light chain optionally associated with the respective heavy chain and the, the antibody heavy chain optionally associated with the respective light chain, said ligand or fragment retains the ligand-receptor binding capability and said chain of said a homomeric receptor or a fragment thereof and said chain of a heteromeric receptor or a fragment thereof retain the ligand-receptor binding capability either by themselves or in an association with a homologic or heterologic chain of said receptor. b) a subunit of a heterodimeric proteinaceous hormone, or fragments thereof which retain the ability of the subunit to form a heterodimer with other subunits thereof; wherein sequences (a) and (b) are bonded directly or through a peptide linker, and in which the sequence (b) in each of said two coexpressed sequences are capable of aggregating to form a dimer complex. 2. A hybrid protein in accordance with claim 1, wherein said sequence (a) is selected from the group consisting of TBP1, TBP2 or fragments thereof still containing the ligand binding domain; the extracellular domain of the IFNα/β receptor or the IFNγ receptor; a gonadotropin receptor or extracellular fragments thereof; antibody light chains or fragments thereof, optionally associated with the respective heavy chains; antibody heavy chains or fragments thereof, optionally associated with the respective light chains; antibody Fab domains; and IL-6, IFN-β, TPO or fragments thereof. 3. A hybrid protein in accordance with claim 1, wherein said sequence (b) is selected from the group consisting of subunits of hCG, FSH, LH, TSH or inhibin, and fragments thereof. 4. A hybrid protein in accordance with claim 1, wherein sequence (a) is linked to the amino terminus of sequence (b). 5. A hybrid protein in accordance with claim 1, wherein sequence (a) is linked to the carboxy terminus of sequence (b). 6. A hybrid protein in accordance with claim 1, wherein said two coexpressed amino acid sequences each include the sequence for TBP1 or the fragment thereof corresponding to amino acid residues 20-161 or 20-190 of TBP1, as sequence (a) and the respective α and β subunits of hCG or fragments thereof, as sequence (b). 7. A hybrid protein in accordance with claim 1, wherein said two coexpressed amino acid sequences each include the extracellular domain of a gonadotropin receptor as sequence (a) and the respective α and β subunits of a gonadotropin as sequence (b). 8. A hybrid protein in accordance with claim 7, wherein said sequence (a) is the FSH receptor extracellular domain and sequence (b) is a subunit of FSH. 9. A hybrid protein in accordance with claim 7, wherein said sequences (a) and (b) are linked with a peptide linker. 10. A hybrid protein in accordance with claim 9, wherein said peptide linker has an enzyme cleavage site. 11. A hybrid protein in accordance with claim 10, wherein said enzyme cleavage site is a thrombin cleavage site. 12. A hybrid protein in accordance with claim 10, wherein said enzyme cleavage site is recognized and cleaved by an enzyme which is found in the ovary. 13. A hybrid protein in accordance with claim 9, wherein said peptide linker serves as a flexible hinge. 14. A hybrid protein in accordance with claim 1, wherein one or more covalent bonds between the two subunits (b) are added. 15. A DNA molecule encoding a hybrid protein in accordance with claim 1. 16. An expression vector containing a DNA molecule in accordance with claim 15. 17. A host cell containing an expression vector in accordance with claim 16 and capable of expressing said hybrid protein. 18. A method for producing hybrid protein comprising culturing a host cell in accordance with claim 17 and recovering the hybrid protein expressed thereby. 19. A pharmaceutical composition comprising a hybrid protein in accordance with claim 1 and a pharmaceutically acceptable carrier and/or excipient. 20. A method for inducing follicular maturation, comprising administering a pharmaceutical composition comprising the hybrid protein of claim 8 to a subject in need thereof.