SAT199 Intrathyroidal Parathyroid Adenomas: A Case Series

Abstract

Abstract Disclosure: B.K. Bowens: None. D. LaChance: None. M.K. Shakir: None. T.D. Hoang: None. Background: Primary hyperparathyroidism (PHPT) is a relatively common condition which affects 1-7 people per 1000. However, intrathyroidal parathyroid adenomas (ITPA) have a prevalence of 1.3% to 6.7%. In this case series, we report 3 cases of ITPA. Case 1: 66-year-old male with a history of PHTP without intervention at initial diagnosis presented to Endocrinology several years after initial diagnosis due to an incidental thyroid nodule on routine CT lung cancer screening. Parathyroid hormone (PTH) level found to be 109.3 from a previous level of 80 (ref 10-55pg/mL) in the setting of mild hypercalcemia and osteopenia. Initial bedside thyroid ultrasound was suggestive of a right ITPA. Parathyroid scan, formal thyroid US and CT gated scan revealed a 1.5cm parathyroid adenoma (PA) posterior to the right superior aspect of the thyroid gland. Fine Needle Aspiration (FNA) was completed with PTH washout of 399.40 pg/mL. Right superior parathyroidectomy confirmed ITPA due to an intrathyroidal parathyroid adenoma Case 2: 44-year-old female presented with 9 months of fatigue and was diagnosed with PHPT. Her PTH level was 167 with a serum calcium of 10.9 (ref 8.5-10.4 mg/dL). CT SPECT with tech-99M sestamibi was positive for a right parathyroid adenoma. Explorative surgery did not localize parathyroid adenoma. Thyroid ultrasound revealed a 9mm hypoechoic lesion in the right inferior lobe with polar artery. FNA of this lesion was completed with PTH washout of 4737 pg/mL. Right hemi-thyroidectomy was completed with resolution of PHTP. Case 3: 54-year-old male with history of PHPT and carcinoma of the right kidney s/p nephrectomy presented with persistent hypercalcemia. Serum calcium of 10.2-11.0 mg/dL and PTH of 160-186 pg/mL. Thyroid US showed a 1.1cm hyperechoic, cystic nodule in the left inferior thyroid lobe. Sestamibi was consistent with ITPA. FNA of left thyroid mass with PTH washout of 2602 pg/mL. Parathyroidectomy with left thyroid lobectomy was completed with resolution of hypercalcemia. Discussion: PHPT is a common endocrinopathy with 85% of cases due to PAs, 15% due to parathyroid hyperplasia, and <1% due to carcinoma. ITPAs have an incidence of 1.3% to 6.7% and are due to improper embryologic migration. Sestamibi parathyroid scan allows for localization of PA and for minimally invasive procedures. Other imaging modalities include SPECT, US, SPECT-CT, and MRI. PTH washout with more than 101 pg/mL confirms the presence of parathyroid tissue or adenoma. Conclusion: This is a rare presentation of a common endocrinopathy. These patients were noted to have PHTP. Initial exploratory neck dissections did not localize. FNA and US were able to confirm IPTAs and hemi-thyroidectomy was needed for definitive management with resolution of PHTP. Presentation: Saturday, June 17, 2023