Your level is high. Some people don't feel well at a TSH of 4. others are just mildly tired with a TSH of 78. The TSH of 78 example is a friend of mine who just felt slightly "tired". She did not seek a doctors advice on her own- a friend told her to get checked out.
Botton line- Each of us reacts differently to an elevation in the TSH.
You may feel terrible at a TSH of almost 16- someone else may not even feel unwell.
How do you feel?
I'm new at this, but I believe TSH above 4.0 is not normal. Some say that TSH above 3.0 is too high and will cause symptoms. Yours at 15.96 seems a little more than "slightly elevated".
I was diagnosed with Hashimoto's through a fine needle aspiration, but currently my TSH levels are not affected.
Others will be better able to answer you and I'm sure they will soon. Hang in there!