Causes of grey hair include:
Normal aging
Genetics
Oxidative stress (eg: smoking)
Deficiency states (notably vitamin B12 and folate)
Anaemia
Autoimmune thyroid disease, hypothyroidism, hyperthyroidism
Vitiligo
Alopecia areata
Pituitary problem
Rare premature aging syndromes (progerias) such as Hutchinson-Gilford, Werner's Syndrome
Are the tests you had done in 2015, the last thyroid tests you've had? If so, it's definitely time to get another set done because a lot of things could have changed in a year. This time, ask to have Free T4 instead of Total T4 and make sure they order the Free T3 again, along with the TSH.
In your last test, the Total T4 was near the top of the range, but most of that would be bound by protein and can't be used, which is why we test for Free (unbound) T4.
Your Free T3 was almost on the floor of the range, indicating hypo and your symptoms correspond with hypo, as well.
I'm sure your pcp was looking mostly at the TSH which is considered "pristine" and which most doctors consider the gold standard in thyroid diagnosis. He probably didn't do more than glance at the FT3 or TT4...
Due to the rapidly graying hair, I'd also recommend that you get vitamin B12 tested as low B12 can cause hair to gray more quickly.
Ugh-typos,sorry!
In addition to above
52 yrs.old & had hysterectomy surgery with ovaries intact on 01/16/15. Then two wks later-
Night sweats,headaches,very dry hair & turned grey almost overnight! Skin is dry,no libido,depression.
(mother had thyroid nodules removed surgically). Rx's estrodiol but stopped taking 2 mo.ago-symptoms no better no worse.