Gender?

The doctor's gender is often questioned, but there are two reasons why we know that in David Tennant's form, he was male:
1. Lady Cassandra commented, "So many parts," when she was living in his body in New Earth
2. When Donna Noble saw his human clone naked in the TARDIS (let's not dwell too long on that) she did not comment on anything out of the ordinary, implying that she expected him to be male, and he was.
However, he himself said that he could regenerate into a woman's form, and we have no strong evidence about Matt Smith's form...

I'll leave you to work out what I'm saying