Low ferritin with normal iron is the early stage iron deficiency.
what if the ferritin in 28 ( 30-400) but the iron is 156 ( 59-158) that is the issue with my son and a elevated tsh 6 but great ft3 ft4 and negative for antibodies. dr said it was ok since he had high iron.
If there is an indicated need to test cortisol levels, the best is diurnal saliva cortisol (four tests at various times of day) A serum cortisol is not very useful.
Iron and ferritin are very similar. Ferritin is a precursor to iron levels, so I recommend testing that first. Ferritin should be about 70 minimum. Low levels can cause symptoms and also adversely affect thyroid hormone metabolism. If the ferritin test is high, the a full iron test panel is needed.
Thyroid hormone resistance is reported to occur only one out of 40 or 50 thousand people. You can read about all aspects in this link.
http://www.yourhormones.info/endocrine_conditions/resistance_to_thyroid_hormone.aspx