You need to know more than TT.
FT, SHBG, DHEAs, E2, LH, TSH, to start with.
FT3, FT4, TT3, TT4, Prolactin, DHT, Cortisol (preferably saliva), D3(active and storage), would also be nice to know.
If you have secondary hypogonadism (low LH) there are many possible reasons: I'll list a few...