Other deficiencies can also cause fatigue.
Low Vit D, low Vit B-12 & Iron come to mind. And it is pretty common for people who are hypo to also be deficient in these vitamins as well.
I would recommend that you get your Thyroid checked and that means these three tests in addition to the Vit D, B-12 & Iron:
TSH
Free T4 (NOT total but Free as there is a Huge difference)
Free T3
You must be specific and adamant to get both the FREE T4 and FREE T3 tests. Otherwise you'll get "total" which is an outdated test and not very useful.
And you might want to check for Hashimoto's which is the most common cause for Hypo in the modern world. For this you would add the following two antibody tests
TPOab
TGab
Hashi's is an auto immune condition where your body immune system thinks your thyroid is a foreign invader and like any good immune system goes about killing it. As a result your own body is literally killing your Thyroid's ability to do its job. Thus the only way to make up for that loss of Thyroid is to take medicine to replace it.
If the cause of these problems is hypothyroidism, then the symptoms will disappear with proper treatment, yes. However, there are many other possible causes, and thyroid treatment will not help if thyroid is functioning normally to begin with.
so most people, when treated correctly, get better with the "fatigue, lack of motivation, lack of interest"? would really like to know if this improves or disappears, as these are the things that bother me most.
Fatigue, lack of motivation, lack of interest are all symptoms of hypo...perhaps the most common of all the symptoms. I doubt there's anyone here on this forum who wasn't fatigued or drowsy when hypo. Other symptoms vary person to person, but this one seems universal just about.
I see... thanks! still wanted to know if overall it's a common side-effect, to be unable / unwilling to get up / do much.
It's impossible to answer your questions. We're all different and respond to treatment differently. It took some of us years to feel truly well again. Others hit the nail on the head the first time and felt better more quickly.
Thyroid treatment is a process because it takes a new dose (or an adjusted dose) 4-6 weeks to reach its full potential in your blood. So, you start taking meds (first dose is an educated guess), wait 4-5 weeks, retest, reevaluate symptoms, adjust the dose and repeat until you are symptom-free.
Depression can be a symptom of hypo. It can also have other causes. You won't know until you treat your thyroid problems.