Good to hear you are getting more testing done and seeing a new Endo. With the iron test, make certain they include FERRETIN. Often they do iron testing, but exclude the ferretin if it's not specifically mentioned. Lucky you were able to boost your ferretin to 71. It takes 3 - 6 months, or for some 12mths, to notice proper hair growth phase if it's due to low iron.
My hair was shedding all over informly, but i did notice right at the front centre area that it was definitely thinning. Why wouldn't it after 7 years worth of shedding

at the moment of have loads of baby hairs everywhere, even in the front, but i know it will take ages to truly see major results, but at least there is sign of hair growth as i was so worried about folicles dying and no more hair growing out ever.
All my hormones testing was done first thing in the morning and was done via a saliva test. I also was tested throughout the day, but that was more so for my cortisol levels to check for adrenal fatigue, which you can develop after long term stress among other things.
Not sure whether you are on birth control pills? If you are, maybe the hormone testing can get a bit skewed as a result of the pill, but i'd think your doctor would have taken that into account?
My hair was shedding big time all year around, except for the coldest 2 months of winter for some odd reason. As soon as the warmer weather began i noticed it shedding more and more as we got closer to summer. Then during the summer months it broke my heart to see how much hair i was losing.
I read on the thyroid board that if your TSH goes up and down and doesnt stay constant that that will also contribute to hair shedding.
I have a book at home called A - Z of Nutrients and i was looking up something and came across Protein and how lack of protein or inability to digest protein leads to anemia and hair loss among other things. That is part of my problem, i eat lots of protein but wasnt digesting it due to lack of enzymes.
It's difficult and you need a lot of patience. At the end of the day it has to either be either iron, thyroid, hormone, birth control pill or digestive related. I haven't come across other things, but i'm sure there likely are other things, but those would be the most common ones.
Let us know how you got with your new doctor and new test results. all the best