Background <p>Gender incongruence is defined as discordance between a&#xa0;person’s gender identity and their birth-assigned sex. One important part of the treatment of gender incongruence is gender-affirming hormone therapy, which aims to suppress secondary sex characteristics of the birth-assigned sex and to induce as well as maintain secondary sex characteristics in accordance with gender identity.</p> Objective <p>Which drugs are used for gender-affirming hormone therapy and which effects, side effects, and long-term risks should be expected?</p> Materials and methods <p>The guidelines of the Endocrine Society, the World Professional Association for Transgender Health, and the American Society of Reproductive Medicine as well as clinical trials evaluating the long-term risks of gender-affirming hormone therapy are discussed.</p> Results <p>Gender-affirming hormone therapy has a&#xa0;beneficial impact on mental health and the quality of life of transgender people. One long-term risk appears to be an increase in mortality due to cardiovascular diseases observed in transwomen in comparison to the general population. This increased mortality is not observed in transmen.</p> Conclusion <p>Providing adequate information about effects, side effects, and long-term risks of gender-affirming hormone therapy is crucial to obtaining informed consent. In addition, transgender people must be informed about the effect of gender-affirming treatment on reproduction, and reproductive options must be explored with the individual prior to initiation of treatment.</p>