Iron is not seen as crucial for thyroid function – and biologically available iron is not always possible.  Real iron measures are often missed as you need to know the iron stores – not just the hemoglobin blood results. Blood tests often are not for iron storage – hemaglobin levels alone are insufficient information.

When the gut function is not strong, iron may not be absorbed, regardless of what is being ingested or is from pills.

Need also to absorb iron – minute traces of minerals – molybdenum and copper and zinc

Start looking to heal your gut. Need more zinc and magnesium as well.
Take bioavailable iron in natural forms – esp organ meats and bone broths, and dark green veggies and egg yolks.

Bioavailabilty.Eat balanced, varied wholefoods.