Bleeding in 1st trimester

This is on behalf of a friend who has thyroid problem. She missed her periods which was supposed to come on 24th Dec. She did home pregnancy test using 2 kits. 1 came strongly positive and other was very weak but positive. On doing blood test, HCG count was low 176mL. Her thyroid stimulating hormone was very high 7.6ml. She started taking prenatal vitamins as suggested by doc and increased dose of thyroid medication as well. Yesterday she had bleeding and her HCG count has reduced to 40mL. She did a home pregnancy test and it came negative. What could this mean?