Taub RL, et al. - Researchers sought to determine how testosterone influences ovulatory suppression in transmasculine individuals. Further, they investigated predictors of ovulation in transmasculine individuals on testosterone and appraised the influence of testosterone on anti-mullerian hormone (AMH). From a community clinic that renders gender-affirming hormone therapy, they enrolled participants who were assigned female at birth and were currently using or seeking to begin masculinizing therapy with injectable testosterone esters (transmasculine individuals). Participants performed a collection of daily urine samples for pregnanediol-3-glucoronide (PdG) testing and daily electronic bleeding diaries completion over a 12-week study period. From July to November 2018, 32 individuals were enrolled; of these, 20 completed the study (14 continuing testosterone users, 6 new users). Median age of 23 (range 18-37) was reported. Forty-one percent (13/32) of participants reported bleeding or spotting during the study period. Observations revealed rapid induction of hypothalamic-pituitary-gonadal suppression by testosterone that results in anovulation in a proportion of new users. Further, the data suggest that some long-term testosterone users break through the hormonal suppression and endure an ovulatory event; this raises the concerns pertaining to the requirement for contraception in transmasculine individuals engaged in sexual intercourse with sperm-producing partners. As overall participants are small in number in this work, they suggest this work as hypothesis-generating and recommend performing larger studies to confirm and clarify these findings.