Buserelin belongs to the group of gonadotrophin releasing hormone (gonadorelin) analogues (LHRH agonist). It acts on the pituitary gland which controls the amount of many different types of hormones (chemical messengers). It alters the amount of hormones, particularly the oestrogens androgens. This alteration of hormone levels can be exploited to treat cancers of the prostate gland, which are stimulated to grow by testosterone. Buserelin lowers the levels of testosterone, which starves the tumour of testosterone and causes it to shrink. Buserelin contains 9 amino acids Glu-His-Trp-Ser-Tyr-D-Ser(tBu)-Leu-Arg-Pro-NHEt and having a molecular weight of 1239.44 Dalton.