Why wont doctors sign the forms for me (Canada)?

Doctors are refusing to do necessary tests in which I have been told are necessary by physicians who are family friends. This is a TSH blood test for thyroid problems and a thyroid scan. I decided to get these tests in the US and pay for them myself but you need to have your doctor's referral to do that. My first doctor did not agree to sign them. I even switched doctors and the new one said he will not do it either. WHY? They wont give me an answer. And they wont give me the necessary tests.