This retrospective cohort study investigates predictors of postoperative hypocalcemia following thyroidectomy procedures at Minia University Hospital over a 10-year period (2014-2024). Postthyroidectomy hypocalcemia is one of the most common complications of thyroid surgery, affecting 20-50% of patients. The study aims to identify demographic, clinical, laboratory, and surgical factors associated with the development of both transient and permanent hypocalcemia. Results will inform risk stratification, patient counseling, and perioperative management strategies.

Hypocalcemia is a frequent complication following thyroidectomy, resulting from inadvertent parathyroid gland injury, removal, or devascularization. While most cases resolve within 6 months (transient hypocalcemia),permanent hypocalcemia occurs in 1-3% of patients and requires lifelong calcium and vitamin D supplementation, significantly impacting quality of life.

This single-center retrospective study will systematically review medical records of all patients who underwent thyroidectomy (total, subtotal, or completion) at Minia University Hospital between January 1, 2014, andDecember 31, 2024. The primary objective is to identify independent predictors of postoperative hypocalcemia using multiple logistic regression analysis.

Data extraction will include:

Demographics: age, gender, BMI Clinical factors: indication for surgery, thyroid disease type, presence of Graves' disease, substernal extension Preoperative laboratory values: calcium, vitamin D, PTH, thyroid function tests Surgical details: extent of thyroidectomy, central/lateral lymph node dissection, surgeon experience,operative time, parathyroid gland identification and autotransplantation Postoperative data: calcium levels (24h, 48h, 1 week, 6 weeks, 3 months, 6 months), PTH levels,supplementation requirements Pathology: thyroid weight, presence of parathyroid tissue in specimen, thyroiditis, malignancy The study will employ robust statistical methods including univariate analysis to screen potential predictors and multiple logistic regression to identify independent risk factors. A clinical risk prediction score will be developed and internally validated using split-sample methodology. Subgroup analyses will examine differences between transient and permanent hypocalcemia and stratify results by extent of surgery and surgeon experience.

Target sample size of 500-600 patients was calculated using G*Power to ensure adequate statistical power(>80%) .

Findings will contribute to evidence-based perioperative protocols, improved patient selection for outpatient thyroidectomy, tailored monitoring strategies, and informed decision-making regarding prophylactic calcium supplementation.

Inclusion Criteria:

• Adult patients aged 18 years or older at time of surgery
• Underwent thyroidectomy at Minia University Hospital
• Availability of medical records with complete surgical and postoperative data
• Documented serum calcium levels measured postoperatively
• Minimum follow-up of 6 months postoperatively or documented outcome status

Exclusion Criteria:

• Age less than 18 years at time of surgery
• Preoperative hypocalcemia (serum calcium <8.0 mg/dL or ionized calcium <1.0 mmol/L)
• Pre-existing parathyroid disorders (primary hyperparathyroidism, hypoparathyroidism, secondary or tertiary hyperparathyroidism)
• Chronic kidney disease Stage 3 or higher (estimated glomerular filtration rate <60 mL/min/1.73m²)
• Malabsorption syndromes affecting calcium metabolism (celiac disease, inflammatory bowel disease,short bowel syndrome)
• Concurrent planned parathyroidectomy
• History of neck irradiation
• Chronic use of medications significantly affecting calcium metabolism (bisphosphonates, denosumab,cinacalcet, chronic corticosteroids)
• Incomplete medical records lacking essential data including surgical details, postoperative calcium levels,or follow-up data
• Patients lost to follow-up before 6-month endpoint without documented outcome status

This retrospective cohort study will include adult patients (aged 18 years and older) who underwent a thyroidectomy procedure at Minia University Hospital, a tertiary care centre in Egypt, between January 1, 2014, and December 31, 2024. The target population consists of approximately 600 consecutive patients who meet the eligibility criteria. This includes patients with available medical records containing complete surgical and postoperative data, documented postoperative serum calcium levels, and a minimum of 6 months of follow-up or a documented outcome status. Patients will be excluded if they have preoperative hypocalcemia, pre-existing parathyroid disorders, chronic kidney disease (Stage 3 or higher), or other conditions that significantly affect calcium metabolism. The study population represents a consecutive sample of all patients meeting these criteria over the 10-year study period at this single academic center.