I know this is scary stuff, I had a "hyper-thyroid" scare just last month. My OB/GYN thought I may have a problem but turned out not to be. However, with my family history it is just a matter of time, so I keep my eye on it.
I have a grandmother on my maternal side and an aunt and uncle on my paternal side that all have Hyper-Thyroidism. It hit all of them very young. mid 20's up to 32. My Aunt was diagnosed with Grave's Disease a few months after the birth of her first child. Pregnancy is often found to be a "pre-cursor" for it.
All of the people in my family with HypER-Thy. had the classic symptoms. Eratic Behavior/Nervous Energy, weight loss, sleeplessness, etc. It hit them all very quickly so I think your daughter must be lucky to have discovered the problem before the physical symptoms get worse.
Being a new mom who wouldn't be tired, hungry and maybe just a little depressed. I can see why she may have thought nothing was wrong.
In my experience, which is just with my family, they usually don't remove the thyroid to treat Hyper-Thyroidism, unless the doctor removes it because of the nodules. It can be treated with medication and I believe by even destroying the thyroid or part of the thyroid to cut down on the production of Thyroid hormones.
From the research I found when I thought I might have Hyper-Thyroid, the Hyper condition is easier to treat than the Hypo- condition. It sounded to me like the most worrisome problem in treating Hyper is possibly cutting down the production of Thyroid Hormones too much and then becoming Hypo-Thyroid, which as I said above, is harder to treat.
Another fact I found from a family doctor a few years ago is that Thyroid disorders and Female problems like Endometriosis often go hand in hand. Often, if someone has Endometriosis the doctor will check to see how the Thyroid is functioning as it may be the cause of the Endometriosis. I have never read this anywhere, but in my experience with my family, both my grandmother and aunt had endometriosis and problematic periods and then later were found to be Hyper-Thyroid.
As I said before. My aunt first started having problems after the birth of her first child and she went on to have two more very healthy children and now that she is 37 she is even talking of having one more. So, you can go on to lead a very healthy life style even with Hyper-thyroid.
My grandmother was diagnosed with Hypo when she was 32 and she is about 67 now. She was treated with the radiation/iodine (sp?) therapy, which I believe is supposed to destroy the thyroid. She has had a pretty normal life too and no other serious conditions except now that she is older she has problems with high BP, Diabetes, etc. which comes with the territory with age in our family.
It is scary to think about surgery, medication, etc. but the people in my family really haven't had many problems resulting from the treatment. I am sure she will be ok. It is very scary to think about, just try to stay calm because once the doctors figure out the appropriate treatment, I'm sure she will be just fine.