For about as long as I can remember I have been irritable, anxious, depressed, sometimes fatigued, and frequently had a hard time focusing. Then, over the years came the diagnoses of Schizoaffective Disorder, Obsessive-compulsive Disorder, Asperger's Syndrome, ADD, and Idiopathic Hypersomnia. (The ADD is questionable because of the overlap of symptoms with other disorders, but I really think I have it.)
Although in the long run, I know doing without this hormone will cause serious problems of fatigue and depression.... when my thyroid went underactive and untreated for a while, I felt better able to focus and less anxious... but that extreme hypothyroidism caused some major problems; for instance, I think I vomited once or twice because of that and probably some of my sleepiness was because of it during that time.
But these days, if I skip my Levothyroxine, I can focus better, feel less anxious/obsessive, feel less irritable, less depressed; I start to get stomach pain, muscle aches, and joint aches. Didn't happen this morning because I didn't have the pills, but did happen this afternoon after I got the Levothyroxine from the pharmacy. Honest. The pattern is not going away. My primary care doctor says it's an imagined thing caused by my anxiety disorder(s). I am pretty convinced it is not caused by that.