Talk to Gynecologist on Pregnancy

21 weeks pregnant.I'm hyperthyroid and taking thyroxin 50mcg frm 1st month of pregnancy.I repeated my thyroid profile last month my Dr said it's in normal range and continued thyroxin 50mcg, in reports my T4 seems raised my question is if TSH is in normal range then why T4 is raised,is it could have any harm to baby's health and how I can control it. My 2nd question is about anomaly scan it should be done btw 16 to 22 weeks of pregnancy,I visited to my gynea at 17 weeks but she didn't suggest me this scan my next appointment is at 22 weeks of when I visit her she do normal well being ultrasound to chk is everything is do I have to go for anomaly scan for myself or w8 tll my next visit?Do anomaly scan is necessary??