First of all what was your TSH level
(High TSH levels) in early pregnancy
can affect baby's brain development, but risk depends on levels of TSH. It can rarely cause miscarriage
. So its better to take eltroxin as advised by your doctor. Regarding precautions, only precaution you have to take is to take medicine (Eltroxin) regularly, early morning & empty stomach. Don't eat anything for at least half hour & don't take any other medicine for at least 4 hours.
Wish you good health.