Thyroid? does it get better after treatment.?

I am 40yrs old and have been getting hot flashes, cant sleep, gained weight, stomach upset, and very very tired. I am a diabetics but the tiredness is not from high blood sugar. My sugars are well controlled. I am going to the doctor today to have my thyroid tested. I am wanting to know how successful treatment has been for others. Also I have been very irritable which is not my normal.