7147 A Retrospective Evaluation of Biochemical and Clinical Criteria of Permanent Hypoparathyroidism After Total Thyroidectomy and Their Associated Outcomes

Abstract Disclosure: D.G. Su: None. S. Tsou: None. W. Shen: None. Q. Duh: None. C. Graves: None. I. Suh: None. Background: Postoperative hypoparathyroidism (hypoPT) is the most common complication of total thyroidectomy and carries long-term morbidity. However, reported incidences vary widely due to nonstandardized measurement practices and absence of a universally accepted definition. This study aims to evaluate various definitions of hypoPT and to identify influencing factors such as diagnosis and operative duration. Methods: We performed a retrospective analysis of patients with a diagnosis of hypoPT (ICD-9: E20, E20.0, E20.8, E20.9, E89.2) between January 2012 and January 2019 at a single large academic institution, and only included those who had underwent a total thyroidectomy six months prior. Definitions based on low parathyroid hormone (PTH) values (PTH < 10 pg/mL), low calcium levels (corrected calcium [Ca] < 8.5 mg/dL or ionized Ca [iCa] < 1.1 mmol/L), and postoperative supplementation (elemental calcium or vitamin D) were evaluated at 6 and 12 months postoperatively. Postoperative hypocalcemic symptoms were graded by disease severity (based on the presence of numbness/paresthesia, muscle spasms/aches, and Chvostek/Trousseau signs). Patient demographics, operative and pathological characteristics, and use of parathyroid autotransplantation were recorded. Results: Of 879 patients with hypoPT ICD-9 diagnoses, 124 (14%) underwent a total thyroidectomy and were included. Our cohort was 64% female with a median age of 52.9 years. Fifty-one patients (41%) had low PTH levels, 49 (39%) had low calcium levels, and only 26 (21%) had both low PTH and calcium. Of 94 patients (76%) with hypocalcemic symptoms, 68 (73%) required long-term calcium or vitamin D supplementation. Twenty-eight (22.6%) patients had either an ED visit or readmission for hypocalcemia postoperatively. One hundred seven patients (86%) had a pathologic diagnosis of malignancy, of which 37% had extrathyroidal extension, 25% vascular invasion, and 36% positive margins. Those who underwent parathyroid autotransplantation (33%) were less likely to meet biochemical definition of hypoPT (p = 0.0312). Dosage of calcium/vitamin D supplementation did not correlate with symptom grade. Conclusions: Postoperative hypocalcemic symptoms and long-term calcium/vitamin D supplementation were the most common characteristics found in our permanent hypoPT cohort. However, substantial heterogeneity in defining postoperative hypoPT exists, with no definition capturing the full spectrum of affected patients. Further research is necessary to develop reliable diagnostic criteria or biomarkers for hypoPT prediction and management. Presentation: 6/2/2024