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In this retrospective study our purpose was to assess whether hormone interventions for gender dysphoria pose additional somatic risks for adolescents. We examined changes in metabolic laboratory parameters, body mass index (BMI), and blood pressure (BP) and analyzed adverse effects during gender-affirming hormonal treatment (GAHT). We analyzed follow-up data on 119 transgender adolescents using GAHT at the adolescent gynecology clinic in Helsinki University Hospital, Finland from January 2010 to January 2022. During the study period, 99 (83%) transgender males and 20 (17%) transgender females started GAHT. The median GAHT follow-up duration was 34.0 (interquartile range 17.2) months. Mean hemoglobin (HB) and hematocrit (HCT) levels increased by 16% (<i>p</i> &lt; 0.001) during testosterone treatment, decreased by 10% (<i>p</i> &lt; 0.01) during estrogen treatment, and plateaued after one year. During the initial follow-up, no clinically relevant changes were seen in glucose and lipid metabolism, BMI, or BP. Adverse effects leading to testosterone dose reduction were reported in 19% of transgender males and were less common when gonadotropin-releasing hormone analog was used in testosterone treatment initiation (11.1% vs. 27.8%, <i>p</i> = 0.04). Somatic adverse effects requiring hospitalization or permanent discontinuation of GAHT were not reported. The somatic changes observed in this study were typical for GAHT. No serious somatic adverse effects occurred. Regular measuring of HB and HCT in transgender males undergoing GAHT is warranted, but excessive monitoring of glucose and lipid metabolism, BMI, and BP during the initial follow-up period may not be necessary for somatically healthy adolescents.