Why after changing LC_CTYPE I cannot display non-ASCII characters?

In order to fix problems with PostgreSQL I have defined my systemwide LC_CTYPE environment variable to "C".
The LC_COLLATE was already defined as "C" since the very first installation.
Now, all programs cannot show properly the non-ASCII characters (like the accented vowels).
Why is this happening even if my "locale" outputs the following:

LANG=it_IT.UTF-8
LC_CTYPE=C
LC_NUMERIC="it_IT.UTF-8"
LC_TIME="it_IT.UTF-8"
LC_COLLATE=C
LC_MONETARY="it_IT.UTF-8"
LC_MESSAGES="it_IT.UTF-8"
LC_PAPER="it_IT.UTF-8"
LC_NAME="it_IT.UTF-8"
LC_ADDRESS="it_IT.UTF-8"
LC_TELEPHONE="it_IT.UTF-8"
LC_MEASUREMENT="it_IT.UTF-8"
LC_IDENTIFICATION="it_IT.UTF-8"
LC_ALL=

as the current setup?

Thanks.