TGYoshi says:
Every week (maybe month) there is LP-balance, and you can lose LP then if you have over 60k LP. At least that's how it worked in TMF.
The idea in TMF was:
100k people could have over 60k LP
10k people could have over 70k LP
1k people could have over 80k LP
100 people could have over 90k LP
Nobody actually had 100k LP, after the reduction the number one was kicked back to 99984. Maybe this helps you