Regarding Hepcidin-based regulation, from what I understand, it is an incomplete blockade with further variation by individual and Iron type. Here is the best quote on the topic I found after a quick search:
The body regulates iron absorption in the gut based on current needs. However, this regulatory system is easily overwhelmed by high, sustained intakes from fortified foods and supplements. When intake persistently exceeds demand, the body keeps absorbing the mineral. [1, 2, 3]
This is also shown by the Hepcidin’s greater (almost double) ability to block non-heme iron vs. heme iron. (This can create an issue for pre-menopausal female vegans.)
More generally, the body appears to be optimized for what we would consider low-to-moderate iron intake, not the much higher intakes that modern food supply allows and, in the case of fortification, essentially mandates for many people. Historically, the best sources of iron would have been much less available than they are today.
Note: AI produces a lot of contradictory and confusing responses to iron-related topics which appears to be due to 1) lack of general awareness of the highly toxic nature of excess iron, and 2) over-reliance on ferritin as an indicator of total-body iron status.
Stepping back, as
@Jim marlow alludes to, the reason I raise this point every time the topic of Iron comes up is because most people seem to wildly over-focus on a specific ferritin number rather than looking at the whole Iron/copper/ferritin/ceruloplasmin topic in general and with recognition of the serious consequences of excess. If an adult male thinks they have low total body Iron and they haven’t been donating blood frequently or running triathalons, the first question needs to be, “where did the iron go and how is that possible” since the iron in the hamburger you ate when you were ten years old is still somewhere in your body. If low ferritin is raised to "normal" from Iron that is released from organs where it shouldn’t be, then the low ferritin (temporarily) is a very good thing if there are no negative symptoms, although there is a lot more going on so that is an oversimplification to make the point that jumping to Iron supplementation should be viewed with great suspicion and IMO as an absolute last resort after copper, food, adjusted
TRT dose and time have all been allowed to function.
More generally, as I’ve reported in other threads, my HCT and (back when I measured it) ferritin have jumped around quite a bit without any symptoms or reason I can identify for the change, so I try to optimize things as best I can and not obsess over a single reading with hopefully a gradually reduction in any Iron overload I build up over decades of not donating blood as my highest priority.