This is well outside my usual area of expertise, and perhaps someone else can come give a response that's more in depth. However I'll give an answer since this is a pretty quick answer and one I happen to have read something on.

tl;dr: Likely not true.

Why? Because there is no significant evidence for these claims. They were first levelled at him by a political opponent, Otto Strasser, and may have simply been a smear campaign. Those writing histories of Hitler who have since brought it up have themselves said that they were just speculating.

There's just not much reason to think the claims were accurate. It's not something that has any real supporting evidence/records.

See:

• Kershaw, Ian (2008). Hitler: A Biography. New York: W. W. Norton & Company

• also see [Sexuality of Adolf Hitler (Wikipedia)] (http://en.wikipedia.org/wiki/Sexuality_of_Adolf_Hitler#CITEREFKershaw2008) for a quick overview