I hit the jackpot at 75mcg (weighing in at 67kgs and 5ft 1in) and went hyper! lol
Now I'm on 50mcg 4 x week and 62.5mcg 3 times a week.
It all depends on drug sensitivity and how fast and good your body absorbs the meds.
They used to often assume coz you were big you needed more dose. My sister was vry overweight with her Grave's disease..so they gave her 270mcgs...needless to say she went into hyper mode real fast...then they opened the books and discovered it goes by TSH etc not the weight...so now she is on a 100mcg dose and doing well.
They normally now start you on the lowest dose first then go from there.
I know a 120 lb woman on more Levoxyl than you. So no, it's not all weight, but they usually start there. Everyone's body is different.