I have an underactive thyroid. I will do fine for a good while then it starts to act up and my endo has to increase my dosage. About a yr ago I started off with only 15mcg Levoxyl and now I am at 100mcg of Synthroid. It just keeps going up. I wanted to wait awhile before I had my third child but now I am wondering if I should start now just in case I may not be able to later on. I am 31 yrs old and time is ticking. I didn't want to have a child after 35.