Yes, ADENOIDS is a Scrabble word!

Letter values in Scrabble US: A 1, D 2, E 1, N 1, O 1, I 1, D 2, S 1.

Is it a valid word?

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

a collection of lymphatic tissue in the throat behind the uvula (on the posterior wall and roof of the nasopharynx)

Also: pharyngeal tonsil, luschka's tonsil, third tonsil, tonsilla pharyngealis, tonsilla adenoidea.