FRI561 The Thyroid Trifecta

Disclosure: P. Kachhadia: None. S. Khan: None. A. Abu Limon: None. S. Aldasouqi: None. Introduction: Autoimmune Hashimoto’s Thyroiditis (HT) and Graves’ Disease (GD) may co-exist or may occur alternatingly, known in many case reports as Graves’s Alternans. Hyperfunctioning (Toxic, hot) thyroid nodules (TN) may also co-exist with GD, a rare condition called Marine-Lenhart syndrome. However, the co-existence of HT, GD and TN is perceivably rarer. Case Presentation: The patient is a 45 year old female with a prior history of HT for 20 years, who presented to the clinic with symptoms of minimal eye pain, tremors, fatigue, diarrhea and anxiety. She was not on thyroid replacement, with normal thyroid function tests (TFTs). Physical exam showed bilateral proptosis, a moderate goiter, hand tremors, mild anxiety and tachycardia. Labs showed high TPO (3995.0 IU/mL, n <18 IU/mL), Thyrotropin receptor antibody (5.25 IU/L, n<1.75 IU/L), and Thyroid-stimulating immunoglobulins (1.8 TSI index, n<1.3 TSI index) with low-normal TSH of 0.42 uIU/mL (0.35-4.01 uIU/mL) , mid-range free triiodothyronine (FT3) at 3.6 pg/mL (2.8-4.4 pg/mL) and normal free thyroxine (FT4) at 0.80 NG/dL (0.61-1.37 NG/dL). Thyroid US showed a 2.4 cm left lobe inferior nodule classified as TI-RADS 3. Fine needle aspiration of this nodule was benign. Radioactive Iodine-123 Uptake Scan showed a hot nodule in the left inferior lobe and with visible uptake in the rest of the gland (uptake was mid-normal). She was started on methimazole 5mg once daily and propranolol 10mg BID with improvement in her symptoms. Subsequent TFTs showed stable T4 and T3 and normalization of TSH to 1.78 uIU/mL (0.35-4.01 uIU/mL). Discussion: Marine-Lenhart syndrome was described in 1911 by surgeons David Marine and Carl Lenhart. Graves’ Alternans has been described in the literature, with variable time separation. Though thyroid nodules occur in up to 35% of those with GD, only 1-4.1% are deemed functional nodules. Nuclear medicine imaging via Tc-99m pertechnetate or I-123 iodine at diagnosis of GD generally shows such nodules as cold nodules lacking uptake, while the rest of the gland has diffuse uptake. However, with normalization of TSH through treatment, these cold nodules may alternate uptake and present as hot nodules. Conclusion: In conclusion, this case presents the co-existence of HT, GD and HN, a term we are calling “Thyroid Trifecta”. It is imperative that HNs should be identified if RAI treatment is planned in such patients. Literature review portrays cases in which if thyrotoxicosis persists post RAI treatment for GD, careful examination and repeat RAIU may show a hot nodule consistent with Marine-Lenhart Syndrome. These patients may benefit instead from thyroidectomy. In the case of our patient, definitive treatment options have been discussed and she has been referred for thyroidectomy due to the presence of the TN. RAI ablation will be avoided in view of mild but active thyroid eye disease. Presentation: Friday, June 16, 2023