Case Report Unusual Presentation of Hypothyroidism in a Pregnant Woman, Mimicking Gestational Trophoblastic Neoplasm Soheila Aminimoghaddam, 1 Narmin Karisani, 2 Maryam Mazloomi, 3 and Maryam Rahimi 3 1 Department of Obstetrics & Gynecology, Firoozgar Hospital, Iran University of Medical Sciences, Tehran, Iran 2 Department of Obstetrics & Gynecology, Shahid Akbar-Abadi Hospital, Iran University of Medical Sciences, Molavi Street, Tehran, Iran 3 Department of Obstetrics & Gynecology, School of Medicine, Shahid Akbar-Abadi Hospital, Iran University of Medical Sciences, Molavi Street, Tehran, Iran Correspondence should be addressed to Narmin Karisani; karisani.n@tak.iums.ac.ir Received 1 December 2015; Revised 14 January 2016; Accepted 1 February 2016 Academic Editor: Annekathryn Goodman Copyright © 2016 Soheila Aminimoghaddam et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Hypothyroidism is a common health issue worldwide with varying clinical manifestations. We report a woman who experienced an incomplete abortion and undiagnosed hypothyroidism who was referred to the oncologist with the suspicion of metastatic gestational trophoblastic neoplasm (GTN). A 29-year-old woman with incomplete abortion was referred to an oncologist for possible GTN due to persistent active vaginal bleeding, an elevated beta human chorionic gonadotropin (hCG), abnormal cervical inspection exam, abnormal liver function tests, ovarian enlargement, ascites, and a pleural efusion. She was found to have hypothyroidism in further work-up. She was managed with thyroid hormone replacement therapy and her condition improved afer 6 weeks. Complete resolution of the ovarian mass and pericardial and pleural efusion was achieved. Tis case describes an important experience; hypothyroidism should be considered in the diferential diagnosis of any woman with an incomplete abortion presenting with an ovarian mass. Evaluation and correct diagnosis are important to prevent mismanagement. 1. Introduction Evaluation of thyroid disease in pregnancy is important for gestational maternal health, obstetric outcome, and subse- quent development of the child. Te most frequent thyroid disorder in pregnancy is hypothyroidism. Maternal hypothy- roidism increases the risk for miscarriage and fetal death [1], anemia, postpartum hemorrhage, placental abruption, car- diac dysfunction [2], gestational hypertension/preeclampsia, and preterm births [1]. Gestational trophoblastic diseases (GTD) are rare com- plications of pregnancy caused by defective diferentiation of the trophoblast. Symptoms difer and may range from uterine bleeding to metabolic disease such as human chorionic gonadotropin (hCG) triggered hyperthyroidism. Metastasis to the lungs and vagina is possible. Additionally, lutein-cysts of the ovaries can occur as a consequence of increased -hCG resulting in ovarian hyperstimulation [3]. Ovarian hyperstimulation syndrome (OHSS) not only happens mostly as an iatrogenic complication of assisted reproductive technology but also occurs following high levels of hCG and severe hypothyroidism [4, 5]. Spontaneous and iatrogenic OHSS share similar pathophysiological sequences including massive recruitment and growth of ovarian fol- licles, extensive luteinization provoked by hCG, and over- secretion of vasogenic molecules by the corpus luteum. Tis can cause acute fuid shifs from the intravascular space to third-space compartments [6, 7]. Due to diferences in the treatment of these diferent diseases, a correct diagnosis is essential [3, 4, 8]. We report a case of hypothyroidism that was initially misdiagnosed and referred to an oncologist with suspicion for metastatic gestational trophoblastic neoplasm. Te history and all laboratory tests must be interpreted with care because misinterpretation can lead to serious consequences for the patient and a delay in treatment. Hindawi Publishing Corporation Case Reports in Oncological Medicine Volume 2016, Article ID 3154267, 4 pages http://dx.doi.org/10.1155/2016/3154267