I think that the best place for me to respond to that question is by mentioning a documentary called White coat rebels. Sorry if I can't provide a link but the one's I know about are considered commercial websites so wouldn't be appropriate to post. One of the experts in the doco states that one of the primary attributes which universities tend to look for in choosing medical students is their level of obedience, rather than intellect or commitment to helping patients. Medical associations keep a tight rein on their union members and, as the doco mentions, senior members of the associations tend to have significant pharmaceutical company connections and don't want the membership going around curing patients, since we are seen as cash cows. When you begin looking at the medical research which is available online you find a massive difference in quality between the highly skilled researchers and the one's who are only funded because of their connections. The best research is around twenty or thirty, if not more, years ahead of standard medical practice because doctors simply aren't allowed to refer to the research in their practices. They actually have to sign a commitment to avoid even speaking about subjects not approved by their medical associations. So you shouldn't be too surprised if standards of medical care aren't particularly high.
As my own standard of medical care, throughout my life, has been particularly substandard I have become increasingly better at trying to understand what is happening in disease. What I have found in looking at medical research is that you get groups of diseases which all share common causal factors so one person's chronic fatigue may relate to one set of diseases while another person's will relate to a completely different set. While I am fairly limited to knowledge of medical research on the subject of just a handful of diseases I have looked at what you are asking because of my own nephrotic syndrome. Firstly you have to understand that copper holds the distinction of being both a heavy metal and an essential nutrient (in small doses). Quite simply, you don't want to have high levels of copper in your body and probably get enough from your diet to cover your needs, though it never hurts to have the occasional food containing high levels.
https://www.eatforhealth.gov.au/nutrient-reference-values/nutrients/copper Doctors always go on about taking iron for deficiencies but I have watched people grow old quickly from such advice. Iron is used in some explosive recipes because of the high oxygen content and flammability it has and this is the same reason that it is a cause of oxidative stress in the body. You can have high levels of it in your blood, causing oxidative stress, and yet still have symptoms of deficiency because your body isn't using it efficiently.
Anyway, because the kidneys and liver are our bodies organs for detoxification it means that almost all of the toxins and heavy metals we are exposed to are going to pass through them at some point.
https://www.eatforhealth.gov.au/nutrient-reference-values/nutrients/copper Medical research connects my own nephrotic syndrome more with cadmium and organic solvents than with other factors. Because of my exposure to engineered silica nanoparticles in my last job I honestly thought that might relate but they seem more likely to damage the kidneys.
https://www.news-medical.net/news/20220829/Inhaling-silica-nanoparticles-can-damage-the-kidneys.aspx I'm sorry to have to tell you that doctors can make up all kinds of excuses to deny patients medical investigations as they have in my own case. I have had specialists describe my local hospitals denials of investigations as suspicious, given all of the facts in my case. In Australia doctors protect their peers at the expense of their patients so one doctors screw up will lead to other doctors refusing the investigations which are likely to expose those mistakes. As for vitamin A and iron metabolism here are a few articles to consider.
https://pubmed.ncbi.nlm.nih.gov/27551308/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3847738/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8835033/ Although a number of other nutrients are required for iron metabolism it is essential to have vitamin A as well but some of our bodies will quickly convert it into retinoids before it can be used in iron metabolism. Since cadmium, which disrupts many processes in our bodies (including increasing conversion of vitamin A to retinoids), is bioaccumulative the older we get the worse its effects on our health.