Yes, MASCULINIZE is a Scrabble word!

Letter values in Scrabble US: M 3, A 1, S 1, C 3, U 1, L 1, I 1, N 1, I 1, Z 10, E 1.

Is it a valid word?

MASCULINIZE is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

give a masculine appearance or character to
produce virilism in or cause to assume masculine characteristics, as through a hormonal imbalance or hormone therapy

Not playable in Scrabble US: VIRILISE.