Table 1. Inclusion and exclusion criteria.

Inclusion criteria	Exclusion criteria
Boys with 47,XXY Klinefelter syndrome verified by conventional chromosome analysis or array CGH.	Previous or ongoing T treatment except for TRT because of micropenis during minipuberty
Age 10 to 14 years at inclusion	Contraindications to TRT
LH > +2 SD by ultrasensitive LH assay	Participation in any other clinical trial
Free T<+2 SD
Signed consent from both parents

.LH, luteinising hormone; T, testosteroneTRTtestosterone replacement therapy