LHRH analogue

any one of a group of analogues of luteinizing hormone releasing hormone, which stimulates the release of luteinizing hormone (LH) from the pituitary gland. LHRH analogues are more powerful than the naturally occurring hormone, initially increasing the secretion of LH by the pituitary: this acts to block the hormone receptors and to inhibit the release of further LH. LHRH analogues, which are also known as GnRH analogues (see gonadotrophin-releasing hormone) or LHRH agonists, are effective in the treatment of endometriosis; administered by depot injection or nasal spray, they ensure ovarian suppression. They are also used to shrink fibroids and in the treatment of some types of infertility. Two LHRH analogues, goserelin (Zoladex) and leuprorelin (Prostap), are increasingly being used in the treatment of advanced prostate cancer. Both are given subcutaneously in depot form into the abdominal wall at one- or three-monthly intervals. After causing an initial rise in plasma testosterone for approximately ten days the level then falls to the same low level as that achieved by castration. Because the initial flare in testosterone may cause an acute enlargement of the cancer, anti-androgen are given at the same time. See also buserelin, gonadorelin.