May I add a couple of links in case it helps anyone? I am not a sufferer but a friend of mine was for several years. I stuck by him through his dark times (several years). He barked at me numerous times, as I tried to offer help. He didn't believe that anything would help. He was so downbeat and weakened that simply having a moment's optimism would be exhausting. I would offer advice from my own research, to which he would immediately scoff at. But he came through it and now he is well.
The small steps. The small percentages. Subtle adjustments are often the most effective. Doctors are told what to think such that they are not able to help. That does not mean its the end.
Chemical imbalances, hormones etc are involved, but the power of mind, emotions, beliefs and how we think, are also involved - good or bad. Guilt. Broken heart. Pressure. And the way we deal with those factors.
My friend knows how he got down to the bottom. Pride, holding onto stress, denial of problems that were piling up. Something popped, eventually.
When he finally let go of the stuff he was clinging onto, or, put another way, all the stuff he was piling on top of himself, he could finally let himself fall or, put another way, dump the huge weight and just leave it where it falls.
Either way, it seemed to help. My friend found an escape. He found a way to clear his clutter and start looking forward. Eventually, the clouds cleared. He hasn't looked back.
One article on low cortisol worth a look if you need back up for your real condition.
Then loads of links here to thyroid based literature.
You are not alone. The condition is being understood(slowly!)