Background: Low T may increase the risk of cardiovascular disease, osteoporosis, and reduced quality of life. T might be reduced by TC, its treatment, ageing, and particularly their combination. Methods: T was retrieved from 311 TCSs after orchiectomy and prior to subsequent management with either surveillance/surgery only (S), radiotherapy (RT) or cisplatin based chemotherapy (CT). Human Chorionic Gonadotropin (hCG) was available for 211 TCSs. T was reassessed at surveys performed 9 (S9) and 18 years (S18) after treatment. T values were categorized into quartiles according to cut-off values derived from 570 healthy controls (C) for each decadal age group. Statistical associations were assessed with Chi² tests. Results: In TCSs about to receive RT or CT, T and hCG were higher when compared to those subsequently managed by S. TCSs were more likely to belong to the lowest T quartile, more so with increasing treatment intensity (table). The proportions of TCSs belonging to the corresponding T quartiles displayed no significant changes from S9 to S18. Conclusions: TCSs had lower T than C of similar age already after orchiectomy, possibly related to removal of the affected testicle and/or testicular dysgenesis syndrome. TCSs who were to receive RT or CT had slightly increased T when compared to S, probably due to hCG stimulation. T reduction by RT or CT has been described previously but rarely in longitudinal studies. Of note, longitudinal assessment of T without comparison to C might result in overestimation of the treatment burden. Relatively stable age adjusted T levels from S9 to S18 for the TCSs independent of treatment are encouraging.

	C: n=570, (100%)	S: n=69, (100%)	RT: n=133, (100%)	CT: n=109, (100%)
Pretreatment
<25%	139 (24.4)	39 (56.5)	62 (46.6)	42 (38.5)
>75%	141 (24.7)	3 (4.3)	18 (13.5)	18 (16.5)
OR(95%CI)	Referent (R)	13.2 (4.0- 43.7)	3.5 (2.0- 6.2)	2.4 (1.3- 4.3)
S 9
<25%	139 (24.4)	28 (40.6)	61 (45.9)	59 (54.1)
>75%	141 (24.7)	9 (13.0)	12 (9.0)	12 (11.0)
OR(95%CI)	R	3.2 (1.4- 7.0)	5.2 (2.7- 10.0)	5.0 (2.6- 9.7)
S18
<25%	139 (24.4)	26 (37.7)	61 (45.9)	67 (61.5)
>75%	141 (24.7)	6 (8.7)	9 (6.8)	10 (9.2)
OR(95%CI)	R	4.4 (1.8- 11.0)	6.9 (3.3- 4.4)	6.8 (3.4- 13.7)