A566 | Journal of the Endocrine Society | doi: 10.1210/jendso/bvaa046 A566 JESOCI, Volume 4, Abstract Supplement, 2020 Diana Rus, BS 1 , Rita Hench, BS 1 , Jose Jalife, MD 1 , Hakan Oral, MD 1 , Elif A. Oral, MD 1 . 1 UNIVERSITY OF MICHIGAN, Ann Arbor, MI, USA, 2 EGE UNIVERSITY, Izmir, Turkey, 3 DOKUZ EYLUL UNIVERSITY, Izmir, Turkey, 4 MERSIN UNIVERSITY, Mersin, Turkey, 5 CELAL BAYAR UNIVERSITY, Manisa, Turkey, 6 ANKARA UNIVERSITY, Ankara, Turkey. SUN-556 Background Pathogenic variants in Lamin A/C (LMNA) gene are the most common monogenic etiology in Familial Partial Lipodystrophy (FPLD) causing FPLD2. LMNA pathogenic variants have been previously associated with cardiomyopathy, familial arrhythmias or conduc- tion system abnormalities independent of lipodystrophy. We aimed to assess cardiac impacts of FPLD, and to ex- plore the extent of overlap between cardiolaminopathies and FPLD. Methods We conducted a retrospective re- view of an established cohort of 122 patients (age range: 13-77, M/F 21/101) with FPLD from Michigan (n = 83) and Turkey (n = 39) with an accessible cardiac evalua- tion. Also, functional syncytia of mature human induced pluripotent stem cell-derived cardiomyocytes (hiPSC- CMs) from a FLPD2 patient was studied for assessment of autonomous rhythm and action potential duration with optical mapping using a voltage sensitive dye. Results In the whole study cohort, 95 (78%) patients had cardiac alterations (25% ischemic heart disease, 36% ar- rhythmia, 16% conduction abnormality, 20% prolonged QT interval, 11% cardiomyopathy, and 15% congestive heart failure). The likelihood of having an arrhythmia (OR; 3.95, 95% CI: 1.49-10.49) and conduction disease (OR: 3.324, 95% CI: 1.33-8.31) was signifcantly higher in patients with LMNA pathogenic variants. Patients with LMNA pathogenic variants were at high risk for atrial fbrillation/futter (OR: 6.77, 95% CI: 1.27- 39.18). The time to frst arrhythmia was signifcantly shorter in the LMNA group with a higher hazard rate of 3.04 (95% CI: 1.29-7.17, p = 0.032). Non-482 LMNA path- ogenic variants were more likely to be associated with cardiac events (vs. 482 LMNA: OR: 4.74, 95% CI: 1.41- 15.98 for arrhythmia; OR: 17.67, 95% CI: 2.44- 127.68 for atrial fbrillation/futter; OR: 5.71, 95% CI: 1.37- 23.76 for conduction disease. hiPSC-CMs from a FPLD2 pa- tient had higher frequency of autonomous activity, and shorter Fridericia corrected action potential duration at 80% repolarization compared to control cardiomyocytes. Furthermore, FPLD2 functional syncytia of mature hiPSC-CMs presented several rhythm alterations such as early after-depolarizations, spontaneous quies- cence and spontaneous tachyarrhythmia; none of those were observed in the control cell lines. Finally, FPLD2 hiPSC-CMs presented signifcantly slower recovery in chronotropic changes induced by isoproterenol exposure; which indicates disrupted beta-adrenergic response. Conclusion Our results suggest the need for vigilant cardiac monitoring in FPLD, especially in patients with FPLD2 who have an increased risk to develop cardiac arrhythmias and conduction system diseases. In ad- dition, study of human induced pluripotent stem cell- derived cardiomyocytes may prove useful to understand the mechanism of cardiac disease and arrhythmias and to create precision therapy opportunities in the future. Thyroid THYROID CANCER CASE REPORTS II Detection of Thyroid Cancer Recurrence in Patients with Positive Thyroglobulin Antibody Receiving Immunoglobulin Therapy. Adeyinka Taiwo, MBBS, Ayotunde Dokun, MD PhD. University of Iowa Hospitals and Clinics, Iowa City, IA, USA. MON-448 Introduction: Differentiated thyroid cancers such as pap- illary and follicular thyroid cancer make up more than 90% of all thyroid cancers. The presence of thyroglobulin autoantibodies makes interpretation of the thyroglobulin level unreliable, as it could be falsely low or falsely high. Studies have shown that rising thyroglobulin antibody levels, could be used to monitor for disease recurrence in patients with negative thyroglobulin and imaging studies. However, there are challenges in detecting recurrence in patients with normal thyroglobulin level and thyroid im- aging studies, who are on lifelong immunoglobulin therapy and who have increasing thyroglobulin antibody levels. Clinical case: A 63 yr old female was found to have an in- cidental left thyroid nodule at age 48yrs from a carotid ul- trasound. She underwent US guided FNA of the thyroid nodule and was found to have papillary thyroid cancer. She had total thyroidectomy a month later, with removal of a 1.4cm primary, with no evidence of extrathyroidal ex- tension, clear margins and no evidence of lymphovascular invasion – Stage T1bN0M0. There was left level 6 neck dis- section with no carcinoma identifed in the 2 lymph nodes removed. She received 105.3 mCi radioactive iodine (RAI) and whole body thyroid scan done 7 days later revealed, increased uptake involving the thyroid bed likely residual thyroid tissue. Activity was noted inferolateral to the right thyroid bed which most likely represents a lymph node. There was no evidence of distant metastasis. She was commenced on levothyroxine post operatively. Her other past medical history is signifcant for idiopathic ur- ticaria and angioedema, immune defciency disorder with low IgG and IgM and asthma. She was commenced on monthly IV immunoglobulins 5yrs post RAI therapy, due to recurrent sinusitis, rhinitis and chronic diarrhea. She was later transitioned to weekly SQ immune globulin – Hizentra which she is on till date. Over the past 15 years, serial neck ultrasounds post radioiodine ablation have been negative for recurrence. Her TSH ranged 14.91 to 0.04 (ref 0.27-4.2 uiu/ml) and thyroglobulin (Tg) titer remains <0.1 (ref <0.1). Her thy- roglobulin antibody titers have trended up from <0.2 (ref <2.0) 5yrs post RAI therapy to 49 (ref <4 iu/ml)) on her most recent test this year. She is currently undergoing further work up to rule out recurrence of her cancer. In our review of the literature we found one report that showed use of Liquid Chromatography–Mass Spectrometry (LC-MS) was able to differentiate thyroid cancer recurrence in an indi- vidual with positive antithyroglobulin antibody receiving immunoglobulin therapy. Conclusion: In patients with negative Tg levels, but elevated thyroglobulin antibody while receiving immune globulin therapy, thyroglobulin antibody levels may not be a reliable indicator of thyroid cancer recurrence. Measurement of Tg levels using a LC-MS may provide some clarity. Downloaded from https://academic.oup.com/jes/article/4/Supplement_1/MON-448/5832838 by guest on 23 September 2020