Decapeptyl SR (Sustained Release) is a synthetic form of a natural hormone known as gonadotropin-releasing hormone (GnRH). It is used in the treatment of hormone-sensitive cancers such as prostate cancer in men and endometriosis, uterine fibroids, and precocious puberty in children. The medication works by initially increasing the levels of certain hormones in the body, but then it drastically reduces their levels, which helps to control the growth of hormone-sensitive tumors or conditions. Decapeptyl SR is administered through injections, and its sustained-release formula allows for the gradual release of the medication into the body over time, reducing the frequency of injections needed. This medication should be used under the supervision of a healthcare professional due to its potential side effects and the need for monitoring during treatment.