You could have cortisol levels which are not optimal.
Personal anecdote : I had high cortisol show up on a couple of saliva tests. I also found it impossible to raise my dose of thyroid hormones high enough to get rid of all my hypo symptoms. When I tried raising dose I got tachycardia (fast heart rate).
I have treated myself with supplements which are supposed to lower cortisol, and the one that has really helped me is Holy Basil, although for a few months I had to take a higher than recommended dose. Other people have success with other things, there is no consistency about what might help and treatment involves trial and error.
Since taking the Holy Basil I have managed to increase my dose of T3 and several of my hypo symptoms have reduced, and my heart rate has been less of a problem.
Please note that low cortisol and high cortisol have symptoms in common, and it isn't possible to guess whether cortisol is high or low based on symptoms alone. Testing is essential. Treating high cortisol with products which raise cortisol, or treating low cortisol with products that lower cortisol, would be disastrous.
Blood tests for cortisol are rarely helpful, but they are the only ones that doctors do. Blood tests won't show levels of cortisol throughout the day, nor do they measure the cortisol which is actually available to the body to use. The best thing for measuring free (unbound) cortisol and checking the circadian rhythm of cortisol output is saliva testing.