Bulie, hi.
I guess the levels that are off are TSH (since you say 4.something...), indicating you are somewhat underactive (ie, high TSH and low T4 (thyroid hormone)) - obviously you'd better confirm this with your doctor
When I did IVF nobody specifically told me that the hormones etc would mean that I required a higher dose of thyroxine to increase my T4 (becuase of the higher estrogen levels - I should have realised but oh well). Anyway, I went to my endocrinologist at about 5.5 weeks and my TSH was about 35 - which is extremely high. Now, untreated hypothyroidism in pregnancy can affect fetal development, but I am happy to report that my DS seems perfectly normal so far....
Hyperthyroidism - ie, hormone levels too high - is more of an issue as far as the risk of miscarriage is concerned.
IF it is TSH and IF it is 4.something then it doesn't sound too dire. Hope that is the case and a small adjustment will fix things.
All the best with your pregnancy