Hypothyroidism causing miscarriages?

Hey everyone. So I had my son October 2018. His pregnancy was normal and healthy. I started trying for a second in August 2020. Since then I have had 3 miscarriages. I get pregnant pretty easily, but my pregnancies stop progressing at 4/5 weeks. First was 4 weeks, second was 5 weeks, and 3rd stopped growing at 5 weeks, but my body didn't recognize it and start bleeding until 10 weeks. The doctor has done some tests and everything is looking normal except my thyroid levels were 4.5. She put me on Synthroid and we're going to try to get my levels down before continuing trying. Has anyone had Hypothyroidism cause multiple early miscarriages? Does anyone have any advice on Hypothyroidism in general? Tia