8483 Changes in kidney hemodynamics during gender-affirming hormone therapy in transgender individuals - findings from the KNIGHT pilot study

Abstract Disclosure: S.A. van Eeghen: None. C. Wiepjes: None. L.L. Pyle: None. M. den Heijer: Research Investigator; Self; Kyowa Kirin. Other; Self; Novartis Pharmaceuticals. P. Bjornstad: Advisory Board Member; Self; AstraZeneca, Bayer, Inc., Boehringer Ingelheim, Novo Nordisk, XORTX. Consulting Fee; Self; AstraZeneca, Bayer, Inc., Boehringer Ingelheim, Bristol-Myers Squibb, Eli Lilly & Company, LG Chemistry, Horizon Pharma, Novo Nordisk, Sanofi. Research Investigator; Self; AstraZeneca, Merck, Horizon Pharma. Other; Self; Bayer, Inc. D. van Raalte: Consulting Fee; Self; AstraZeneca, Bayer, Inc., Boehringer Ingelheim, Eli Lilly & Company, Merck, Sanofi, MSD. Research Investigator; Self; AstraZeneca, Boehringer Ingelheim, Eli Lilly & Company, Merck, Sanofi, MSD. N.J. Nokoff: Consulting Fee; Self; Neurocrine Biosciences, Inc, Ionis Pharmaceuticals Inc.. Research Investigator; Self; Neurocrine Biosciences, Inc. Other; Self; World Athletics. Background: Studies in transgender individuals have shown that gender-affirming hormone therapy (GAHT) impacts estimated glomerular filtration rate (eGFR). Masculinizing hormone therapy decreases, while feminizing hormone therapy increases eGFR, based on changes in serum creatinine and cystatin C. These substantial changes suggest an effect of sex hormones on kidney hemodynamics. To investigate this, we studied kidney hemodynamic changes before and after 3 months of gender-affirming hormone therapy (GAHT) in transgender individuals. Methods: This prospective observational pilot study assessed kidney hemodynamics in 23 transgender individuals assigned male at birth receiving feminizing hormone therapy and 21 transgender individuals assigned female at birth receiving masculinizing hormone therapy. Feminizing therapy included transdermal (n=16), sublingual (n=5), or oral estradiol (n=2), in combination with an anti-androgen (n=22); intramuscular triptorelin (n=16), spironolactone (n=5) or finasteride (n=1). Masculinizing therapy involved transdermal (n=17) or injected testosterone (n=4). Measures included glomerular filtration rate (GFR; Iohexol clearance), effective renal plasma flow (ERPF; p-aminohippurate clearance), and renal vascular resistance (RVR; mean arterial pressure/renal blood flow). Glomerular hydraulic pressure (PGLO), and afferent/efferent vascular resistance (RA/RE) were estimated by Gomez equations. Linear mixed models compared baseline and three-month measurements. Results: Individuals undergoing feminizing hormone therapy [median age 21 (IQR 19-29) years, BMI median 22.9 (IQR 18.9-30.7) kg/m²] had increased GFR by 2.8 mL/min per 1.73m² (95% CI, 0.01 to 5.6) and a nonsignificant increase in ERPF (+42 mL/min per 1.73m²; 95% CI, -5 to 90). RVR and RA significantly decreased [RVR: -0.007 mmHg/L/min (95% CI, -0.015 to -0.0003), RA: -294 dyn/s per cm5 (5% CI, -568 to -21)], indicating afferent vasodilation. In contrast, individuals receiving masculinizing therapy (median age median 20 (IQR 18-23) years, BMI median 24.2 (IQR 21.1-27.3) kg/m²) showed a slight, nonsignificant decrease in GFR (-2.1 mL/min per 1.73m²; 95% CI, -4.9 to 0.8), with no changes in other kidney hemodynamic parameters. Conclusions: In this cohort of transgender individuals, GFR increased during feminizing hormone therapy, likely due to afferent vasodilatation, while during masculinizing hormone therapy GFR tended to decrease. These findings suggest an influence of sex hormones on kidney hemodynamics, especially during feminizing hormone therapy. Presentation: 6/3/2024