This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
Gestational hypehyroidism occurs due to 
Select and explain. 
A. Beta HCG from placenta, B. Trans-placental transfer of TSH, C. TPO antibodies, D. Anti thyroglobulin antibody
A: Beta HCG from placenta
Answer: A: Beta HCG from placenta 
Explanation: A common cause of overactive thyroid in pregnant women is Graves' disease. This disease occurs when your immune system becomes overactive and forms antibodies (immune proteins) that attack the thyroid. This causes the gland to enlarge and make too much thyroid hormone. Most women with Graves' disease find out they have it and get treatment before they become pregnant. Women with severe nausea and vomiting or those expecting twins may develop temporary hypehyroidism. Called transient gestational thyrotoxicosis, this hypehyroidism is due to high levels of a pregnancy hormone called human chorionic gonadotropin or hCG. Because it resolves by week 14 to 18 of pregnancy, women do not need antithyroid drugs to treat this condition. Ref - pubmed.com