The invention relates to monoclonal antibody capable of specific binding to the molecular weight of 20 kDa variant of human growth hormone. This monoclonal antibody has no substantial binding to hGH of molecular weight 22 kDa. The invention also relates to the use of this monoclonal antibody for measurement of hGH 20K, especially in bo dy fluids. The antibodies can be used for detection and quantification of hGH 20K, especially in serum.
1. A monoclonal antibody specific to human growth hormone (hGH) with molecular weight 20kDa (hGH 20K), the monoclonal antibody having an affinity for hGH 20K of 1 x 10<8> M<-1> or greater and having a cross reactivity of less than 5 % with hGH with molecular weight 22kDa (hGH 22K), wherein the monoclonal antibody recognizes the conformational epitope recognized by mAb-33 produced by the hybridoma cell line deposited as DSM ACC 2254. 2. Monoclonal antibody according to claim I having an affinity for hGH 20K of at least 1 x 10<9> m<-1> and more preferably more than 2 x 10<9> M<-1> . 3. Use of the monoclonal antibody according to any of claims 1 to 2 for in vitro measurement of hGH 20K. 4. Use according to claim 3 for in vitro measurement in body fluids. 5. Use according to claim 4 for measurement in serum. 6. Use according to any of claims 4 to 5 in multianalytic assay. 7. Use of the monoclonal antibody according to any of claims 1 to 2 for purification of preparations containing hGH 20K. 8. Method for immunoassay detection and quantification of hGH 20K comprising the steps of: 1) contacting a sample containing hGH 20K with the antibody according to any of claims 1 to 2 as to form a complex between the antibody and hGH 20K in an amount that is related to the amount of hGH 20K and the sample, and 2) determining the amount of complex formed in a manner known per se and relating the amount found to the amount of hGH 20K in the sample. 9. A therapeutic composition comprising a therapeutically effective amount of the monoclonal antibody according to any of claims 1 to 2 in a pharmaceutically acceptable carrier substance. 10. A hybridoma cell line which produces a monoclonal antibody according to claim 1.