No reason you can't ask your GP; heck you can ask them darn near anything. Depending on what they feel comfortable treating, they'll prescribe or refer you to someone they think is better qualified to handle your case.
Often enough, if you just tell them you feel most comfortable with them managing your health, they'll proceed themselves. I've had my GP do lots of stuff others seem to want specialists for, with no measurable difference in quality of care as far as I can tell.