Added value today of hormonal measurements in ovarian stimulation in gonadotropin-releasing hormone antagonist treatment cyclePopovic-Todorovic, Biljana; Racca, Annalisa; Blockeel, ChristopheCurrent Opinion in Obstetrics and Gynecology: June 2018 - Volume 30 - Issue 3 - p 145–150 doi: 10.1097/GCO.0000000000000459 FERTILITY, IVF AND REPRODUCTIVE GENETICS: Edited by Emre Seli and Juan A. García-Velasco Buy SDC Abstract Author InformationAuthors Article MetricsMetrics Purpose of review Traditional approach of ovarian stimulation monitoring for in-vitro fertilization involves transvaginal sonography and serum estradiol measurements. Accumulating evidence has shown that hormonal evaluations during ovarian stimulation allow individual cycle optimization, moving away from only predicting the risk of ovarian hyperstimulation syndrome, but in addition assessing the impact of ovarian stimulation on endometrial receptivity, quality of oocytes, and subsequently embryos. The purpose of this review is to discuss the relevance and added value of hormonal monitoring during ovarian stimulation in gonadotropin-releasing hormone antagonist cycles where most of the advances have occurred. Recent findings Basal hormonal status, particularly estradiol, progesterone, and luteinizing hormone are instrumental in prediction of the patients with poor prognosis. Estradiol levels on the day of trigger are less sensitive in predicting ovarian hyperstimulation syndrome then the number of follicles more than 11 mm in diameter. Progesterone elevation on the day of trigger is associated with lower pregnancy rates. The gold standard treatment for progesterone elevation is to adopt a freeze-all strategy when the threshold of 1.50 ng/ml is exceeded. The effect of progesterone elevation on embryo quality remains to be confirmed by more trials. Summary Endocrine monitoring during ovarian stimulation allows fine-tuning of the physiology of the stimulated cycle and thereby increases the chances of successful treatment outcome. Centre for Reproductive Medicine, Universitair Ziekenhuis Brussel, Jette Brussels, Belgium Correspondence to Biljana Popovic-Todorovic, Centre for Reproductive Medicine, Universitair Ziekenhuis Brussel, Jette Belgium. E-mails: Popovic-Todorovic@uzbrussel.be (B.P.-T.) and Christophe.Blockeel@uzbrussel.be (C.B.) Copyright © 2018 YEAR Wolters Kluwer Health, Inc. All rights reserved.