The GMC have really taken the judgement of the Supreme Court to heart. They make it clear that patients with the capacity to make decisions make their own decisions about their health. The GMC say:
"Where an adult patient has capacity, and unless they are subject to specific legislation that restricts their ability to make decisions (see paragraphs 104–107), they have the right to make their own decisions about their care, and they can do so in consultation with people of their choosing. "
The guidance even goes further, by stating that patients can make their own decisions in consultation with people of their own choosing. So I take this to mean that patients can consult patient support groups such as Thyroid UK.
However, this is temepred with additional advice to doctors:
"If a patient asks for treatment or care that you don’t think would be beneficial to them, you should explore the patient’s reasons for requesting it. When assessing any likely benefit, you should take into account factors that are significant to the patient, including non-clinical factors such as the patient’s beliefs or views and the possible effect on their lifestyle. If after further discussion you still consider that it would not be of benefit to the patient, you do not have to provide the treatment or care. But you should explain your reasons to the patient and explain any other options that might be available, including the option to seek a second opinion".
This applies to our case, for example when doctors will not prescribe T4 if TSH is in the reference range. It does however, advise doctors that they should explore your reasoning for requesting T4 (to continue the example). To my mind this is where the patient produces the evidence from this site, Paul Robinson's books, other internet sites etc. in compliance with paragraph 9.
The draft guidance gives the doctor permission to refuse to provide care if s/he doesn't believe the evidence. That is a discussion for a different post.