1kg = 2.2 lbs
So, 53kg = 116lbs
1.78m = 5' 10"
Yes, that's pretty light, imho. I'd expect a woman that tall to be 140-150lbs (64-68 kg)
I'm 6' (1.8m) and 240 (110kg), but could stand to lose 60 lbs without looking like I'm starving. So, 180 lbs = 82kg...
"Ideal" height/weight source...5' 8" varies between 126 and 167lbs (
57kg and 76kg), depending on if you have a small, medium, or large frame.
Mine varies between 138 and 179, which is just under my preferred weight of 180 (I have a large frame).
Of course, if you're healthy at your weight--not fatigued, sick, etc--you're fine. But, if you want more curves, you're gonna need to put on perhaps 5-10kg.
fwiw, I don't think excess fat makes the body produce more testosterone.