Background: Hypogonadism, i.e., low T-, high LH- and/or FSH-levels, is frequently observed in TCSs and is associated with cardiovascular disease, osteoporosis and reduced quality of life. Little is known about the impact of aging on hypogonadism in TCSs. Methods: T, LH, and FSH levels were retrieved twice from 874 TCSs median 11 (S11) and 19 (S19) years after orchiectomy and categorized based on cut-offs calculated from 570 healthy controls (C), separately for each decadal age group. Treatment was categorized into surgery (S), radiotherapy (RT) or cisplatin-based chemotherapy (CT). Impact of treatment and aging on T, LH and FSH levels was assessed by comparing proportions of TCSs grouped into the C quartiles by ordinal logistic regression and expressed with odds ratios (OR) and 95% confidence interval (CI). Results: TCSs had lower T and higher LH and FSH levels than C at S11 and S19 (p<0.05, except for LH after S at S11) (Table).Approximately 50% of TCSs had T levels in the lowestquartile at S11 and S19. The proportion of TCSs with T below the 2.5% cut-off threshold for C increased from S11 to S19, for the S (9.7 - 12.5%), RT (9.4 - 16.3%) and CT group (12.5- 19.9%). Conclusions: TCSs had lower T and higher LH and FSH levels than C of similar age indicating an impact of treatment. Importantly, proportions of TCSs in the highest LH quartile and below the 2.5% cut-off for T-level increased from S11 to S19, indicating an accelerated hormonal aging. Continued follow-up of hormone levels is important.