Hashimoto/Hypothyroid and Pregnancy?

Recently I miscarried and a few days later was told I had hypothyroidism. I underwent many tests and I have Hashimoto's Disease. This is the primary cause of my miscarriage according to my doctors. When my husband told his family that I lost the baby due to my thyroid issues they were skeptical saying that one thing has nothing to do with the other and the thyroid is useless like an appendix. Well... it's been several weeks now and my meds are working my TSH is lowering and stablizing and my husband's sister in law called to say that her friend has had her thyroid removed entirely and does not take any meds (not synthroid or cytomel or levothyroxine, NOTHING) and she's 7 months pregnant with a healthy baby and never had a miscarriage threat. Is this BS? I thought if you had no thyroid you MUST be on meds. Am I wrong? Could my docs be wrong? Or is his sister in law just trying to stir s hi t up? I wouldn't be surprised if she was... What do you think? Is it possible? Can you be 7 months pregnant with no thyroid at all and no replacement meds?