Clinically Relevant Laboratory Monitoring of Gender-Affirming Hormone Therapy in Transgender People-Experiences from a Teaching Hospital in the Netherlands.

Background: Transgender care is shifting from academic to nonacademic settings leading to use of common (immunoassay) compared to sophisticated (mass spectrometry) methods to monitor estradiol and testosterone during gender-affirming hormone therapy (GAHT). The type of assay can influence results and have significant implications for clinical decision making. An evidence gap is present in recommendations regarding the assay needed to monitor GAHT. The present study aimed to summarize current evidence and evaluate immunoassay estradiol and testosterone concentrations in transgender people visiting a nonacademic hospital for GAHT.

Methods: Clinical practice guidelines on GAHT and scientific literature on assay methodologies were screened and summarized. Laboratory and medical data from 252 patients who visited the transgender outpatient clinic of the Maasstad Hospital for GAHT between 2020 and 2022 were retrospectively analyzed.

Results: Our research showed that the most used clinical practice guidelines for GAHT provide hormonal target values without recommending a preferred method. A comprehensive literature search on agreement between immunoassay and mass spectrometry showed substantial heterogeneity in results. Retrospective analysis of our immunoassay measured data in transgender people showed hormonal changes during GAHT that are to be expected from the medication used.

Conclusions: We demonstrate that laboratory monitoring of GAHT in a nonacademic hospital can be done safely by immunoassay in most cases. Only in cases where clinical observation is discordant with the hormonal results do more sophisticated methods need to be deployed. A best practice model was proposed for transgender care in nonacademic hospitals.