The bi-directional effects of hormone therapy (HT) and preexposure prophylaxis (PrEP) among transgender (TG) individuals have been examined but the evaluation periods have been short with small cohorts and mixed results.
The iTAB plus Motivational Interviewing for PrEP Adherence in Transgender Individuals (ImPrEPT) study was a parallel two arm RCT of adherence in TG individuals, using individualized Texting for Adherence Building (iTAB) with and without brief motivational interviewing over 48 weeks for PrEP adherence. Individuals agreeing to participate in the hormone sub-study had tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) and sex hormones in serum measured at weeks 0 and 12 and surveys about desired hormone effects and satisfaction with HT at weeks 0 and 24. For this analysis, TG women and non-binary individuals assigned male at birth were grouped as transgender women (TGW) and TG men and non-binary individuals assigned female at birth were grouped as transgender men (TGM). Wilcoxon statistical tests and linear regression adjusting for confounding factors were used to determine differences in TFV-DP in TG on and off HT as well as hormone concentrations and changes in satisfaction with HT gender-affirming traits over time.
Between 6/2017 and 9/2020, 255 TG individuals were randomized in the main study with n=172 individuals enrolling in the hormone sub-study. Mean age was 38 (range 18-58) with 15% Black, 44% White and 34% Latinx. Among 91 TGW on stable estrogen, estradiol concentrations did not change significantly between Week 0 and 12 in individuals taking PrEP (252.4 vs 222.3 pg/mL, p=0.81). Among 60 TGM on stable testosterone, total testosterone concentrations did not change significantly between Week 0 and 12 in individuals taking PrEP (352.7 vs 266.2 ng/dL, p=0.84). At week 12, there was no difference in TFV-DP in TGW not taking HT (n=28) compared to taking HT (n=75) (est. difference of -27.3 fmol/p, p=0.89), and TGM not taking HT (n=11) compared to taking HT (n=43) (est. difference of 505.3 fmol/p, p=0.17), adjusting for confounding factors. There were no changes in satisfaction with or desired physical effects from HT on gender transition (Table 1).
Transgender individuals both on and off HT had similar TFV-DP concentrations in DBS after 12 weeks of daily reported FTC/TDF PrEP use. Serum hormone concentrations were not affected by FTC/TDF PrEP use, and there were no changes in the perceived effect on HT in those taking PrEP.