I keep my nails shortish as I'm a 10 finger typist.
My nails grow like heck I have to file them every week. It's due
to the prescription calcium supplements I have to take (due to hypo para thyroidism,
its not a thyroid problem it's a para thyroid problem - it controls calcium absorbation
in the body mine doesnt work so I have to take lots of calcium to maintain my blood
calcium levels).
Anyway if you want fast growing nails (and hair) try getting more calcium into
your diet.