**1. Introduction**

482 Endometriosis - Basic Concepts and Current Research Trends

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Uterine leiomyoma and adenomyosis represent the most common benign tumors of the female reproductive system (Levy, 2008; Parker, 2007; Sankaran & Manyonda, 2008). These tumors are estrogen dependent, develop during the reproductive period, and are suppressed with menopause. Traditional treatments for myomas and adenomyosis have been various types of surgical techniques. Medical management of these tumors is an approach that has been used recently and is attractive for many gynecologists because of its relative ease and lack of complications (pelvic organ adhesion) compared with surgery. Indications for therapy are similar to those for surgical removal of these tumors and focus on preserving fertility and/or the patient's desire to maintain her uterus. Medications used include androgens, antiprogestogens (mifepristone), raloxifen, and gonadotropin-releasing hormone agonist (GnRHa) (Levy, 2008; Parker, 2007; Sankaran & Manyonda, 2008; Schweppe, 1999). At present, considering efficiency and safety issues, none of the above agents obtained adequate popularity except for GnRHa. However, GnRHa also have disadvantages including bone loss and menopausal symptoms. The effect of GnRHa is transient and reversal of estrogen deprivation occurs soon after discontinuation of the GnRHa and most myoma and adenomyosis returns to their initial size within several months after discontinuation.

Dienogest is a selective progestin that combines the pharmacologic properties of 19 norprogestins and progesterone derivatives, offering potent progestogenic effects without androgenic, mineral corticoid, or glucocorticoid activity (Harada & Taniguchi, 2010; Sasagawa *et al*, 2008; Sitruk-Ware, 2006). Previous trials demonstrated that dienogest provides effective reductions in endometriosis-associated pelvic pain and laparoscopic measures of pathology (Harada *et al*, 2009; Köhler *et al*, 2010; Schindler *et al*, 2006; Strowitzki *et al*, 2010b). Recently, the new progesterone 2 mg daily demonstrated equivalent efficacy to GnRHa (e.g. buserelin acetate and leuprolide acetate) for relieving the pain of endometriosis in two 24-week, randomized studies (Harada *et al*, 2009; Strowitzki *et al*, 2010a; Strowitzki *et al*, 2010b). Because uterine myoma/adenomyosis and endometriosis have many common

<sup>\*</sup> Corresponding author: Institute of Endocrine-Related Cancer, Matsunami General Hospital, Kasamatsu, Japan.

Sequential Management with Gonadotropin-Releasing Hormone Agonist
