In a cross-sectional study of 54 patients with adolescence-onset hypogonadism (33 females, 21 males; age range: 19-40 years), medical care, quality of life, and health status were assessed. Most patients had received adequate medical care with short cumulative periods of interruption of hormone replacement. The prevalence of the metabolic syndrome was 27% in females and 19% in males. In comparison to the general population, females had both a lower bone mineral density (dual-energy X-ray absorptiometry, Z-score=-0.8, p<0.001) and a higher prevalence of obesity (age 19-29 years: study population 35%, general population 4%). The body fat percentage (dual-energy X-ray absorptiometry) was significantly elevated (age 19-29 years: females Z-score=+1.8, p<0.001, males Z-score=+2.4, p=0.001). Quality of life (SF-36) was normal. Despite adequate treatment, patients with early-onset hypogonadism are prone to develop signs and symptoms consistent with inadequate hormone replacement. A successful transition from pediatric to adult medicine seems important to optimize treatment outcomes.