Pregnancy can affect the thyroid hormone level itself but HCG is the hormone that gives a positive pregnancy test result. TSH is the hormone that you are concerned with with graves disease. HCG can cause your thyroid levels to be lower in pregnancy. It is very important if you are pregnant to get in to your doctor immediately because the baby cannot regulate his thyroid hormone in the first 10-12 weeks of pregnancy. Their body does not take over that until after that point. Women with your condition while pregnant are at greater risk for high blood pressure, miscarriage, preterm labor, intrauterine growth retardation and still birth. You need to be followed closely by both your OB and your endocrinologist. My doctor has told me that the tests on the market today are good...and bad. They test so early that sometimes they pick up on conception before implantation even is solidly finished. Many women in years past miscarried early on and never knew it. Their period arrived and it was slightly heavier than normal. But they never knew they were pregnant. Today we can test before our period is even due. So many women experience the sadness of miscarriage when years before they never would have known. If you waited a few days to get that blood work, your levels could have been so low they did not consider it a viable pregnancy and therefor said it was negative. But your thyroid hormone would not affect the pregnancy hormone. Hugs! Good luck and best wishes.

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Yes, my doctor told me the same thing. I trust him completely as I have rare internal defects that only this doctor was able to manage well. Along with those, I have a thyroid deficiency that comes and goes without medication. Just like you, I also took several home pregnancy tests. 3 were positive. 2 were negative. I was sure I was pregnant. The doctor did an ultrasound but no heartbeat was present. Then he did a blood test. No pregnancy indicators there either. At that point, he told me my thyroid was probably fluctuating and explained that thyroid imbalances DO affect urine pregnancy tests.