GnRH agonists are peptides similar in structure to GnRH with amino acid substitutions that enhance their affinity for binding to the receptor, which causes continuous stimulation, initially producing an increase in the release of gonadotropins (flare effect) that can last 1 to 2 weeks, after which gonadal sex steroids decrease until reaching medical castration levels (8). 

The resulting hypoestrogenism can cause complications such as hot flashes, hot flashes, vaginal dryness, bone mass affectation, among others. For this reason, GnRH agnostic should not be used for a prolonged period of time (19). As an alternative, an adjuvant substitutive treatment or add back strategy can be applied. A Cochrane study showed that tibolone, raloxifene, estriol and ipriflavone help preserve bone density and that medroxyprogesterone acetate (MPA) and tibolone can reduce vasomotor symptoms. Some drugs used as MPA, tibolone and conjugated estrogens had as an adverse event an increase in uterine volume (20).

A meta-analysis published in 2020 that included 213 women undergoing myomectomy by hysteroscopy showed no statistically significant difference in the use of GnRH-a compared to the control group for complete resection of submucosal myoma (RR: 0.94, 95% CI: 0.80 to 1. 11); operative time (mean difference MD: - 3.81, 95% CI: - 3.81 to 2.13); fluid absorption (MD: - 65.90, 95% CI: - 9.75 to 2.13); or complications (RR 0.92, 95% CI: 0.18 to 4.82) so the authors do not recommend routine preoperative use of GnRH-a in these cases (21).