IS THERE A RELATIONSHIP BETWEEN VITAMIN D STATUS AND HYPOCALCEMIA AFTER TOTAL THYROIDECTOMY?

Risk Factors for Calcium-Phosphate Disorders after Thyroid Surgery

INTRODUCTION

Iatrogenic hypoparathyroidism following thyroidectomy is one of the most common complications significantly reducing patients' quality of life.

OBJECTIVES

This study aimed to analyze the risk factors for calcium-phosphate disorders following thyroidectomy.

PATIENTS AND METHODS

The study group consisted of 211 patients who underwent thyroidectomy for different conditions in 2018-2020. Demographic, clinical and surgical risk factors were analyzed against hypoparathyroidism and hypocalcemia.

RESULTS

Hypoparathyroidism occurred in 15.63% of patients, and hypocalcemia occurred in 45% of those operated on. There was statistical significance between hypoparathyroidism and the extent of thyroid surgery: thyroidectomy vs. lobectomy (p = 0.02, OR = 4.5) and surgeon experience (p = 0.016, OR = 6.9). Low preoperative PTH levels were associated with a higher incidence of hypoparathyroidism (p = 0.055, OR = 0.9). There was a statistically significant correlation between the occurrence of hypocalcemia and preoperative vitamin D deficiency (p = 0.04, OR = 3.5). Low calcium levels before surgery were associated with a higher incidence of hypocalcemia (p = 0.051, OR = 0.5). Meta-analyses of selected risk factors confirmed that the most significant factor in the incidence of hypocalcemia was a decrease in PTH levels (p < 0.001).

CONCLUSIONS

The extent of thyroid surgery and the experience of the surgeon are the most significant risk factors for hypoparathyroidism. Hypocalcemia is much more common than hypoparathyroidism. Among the risk factors for hypocalcemia, in addition to the decrease in parathormone levels due to iatrogenic parathyroid damage, we should mention vitamin D deficiency in the preoperative period.

Preoperative vitamin D level is significantly associated with hypocalcemia after total thyroidectomy

BACKGROUND

To evaluate the association of preoperative vitamin D levels with postoperative hypocalcaemia after total thyroidectomy.

METHODS

The medical records of patients who underwent total thyroidectomy between May 2020 and January 2022 and who had a documented preoperative serum 25-hydroxyvitamin D (25-OHD) concentration were retrospectively reviewed. Vitamin D levels were categorized into four groups: <10 ng/mL (severe vitamin D deficiency), 10-20 ng/mL (vitamin D deficiency), 20-30 ng/mL (vitamin D insufficiency), and > 30 ng/mL (vitamin D sufficiency). Multivariate logistic regression was performed to analyse the association of vitamin D levels with the risk of hypocalcaemia after controlling for potential confounding factors.

RESULTS

A total of 196 patients were included in this study. Of these, 47 (24.0%) had preoperative 25-OHD < 10 ng/mL, 62 (31.6%) had 25-OHD of 10-20 ng/mL, 51 (26.0%) had 25-OHD of 20-30 ng/mL and the remaining 36 (18.4%) had 25-OHD > 30 ng/mL. The incidence of postoperative hypocalcemia was highest in the group of patients with severe vitamin D deficiency (42.6% and 23.4% for postoperative laboratory and symptomatic hypocalcaemia, respectively), followed by the group with vitamin D deficiency (29.0% and 16.1%), the group with vitamin D insufficiency (19.6% and 5.9%) and the group with vitamin D sufficiency (5.6% and 2.8%). Multivariate logistic regression indicated that the odds of postoperative laboratory hypocalcaemia for patients with severe vitamin D deficiency and vitamin D deficiency were 13.20 times (95% CI: 2.69-64.79, P < 0.01) and 6.32 times (95% CI: 1.32-30.28, P = 0.02) greater than for those with vitamin D sufficiency, respectively; while the odds of symptomatic hypocalcaemia for patients with severe vitamin D deficiency was 10.18 times (95% CI: 1.14-90.86, P = 0.04) greater than for those with vitamin D sufficiency.

CONCLUSION

Preoperative vitamin D deficiency (< 20 ng/mL), especially severe vitamin D deficiency (< 10 ng/mL), is an independent predictive factor of postoperative hypocalcaemia after total thyroidectomy.

Outcome of parathyroid function after total thyroidectomy when calcium supplementation is administered routinely versus exclusively to symptomatic patients: A prospective randomized clinical trial

PURPOSE

Current guidelines for calcium supplementation for parathyroid function recovery after thyroidectomy are based on low-quality evidence. The present trial compared the effects of oral calcium and vitamin D supplementation on the recovery of parathyroid function when administered routinely or exclusively to symptomatic patients.

METHODS

This prospective, randomized, open-label clinical trial analyzed 203 patients who underwent total thyroidectomy and developed hypoparathyroidism on postoperative day 1 (POD1) with median age of 41 years and proportion of women of 77.8%. Participants were randomized to group A (calcium and vitamin D supplementation administered only to symptomatic patients) and group B (routine supplementation). The primary outcome was the incidence of protracted hypoparathyroidism in the two groups. Secondary outcomes included risk factors for postoperative protracted hypoparathyroidism and the incidence of symptomatic hypocalcemia.

RESULTS

The incidence of protracted hypoparathyroidism was not significantly different between group A and group B (11 of 99 vs. 17 of 104, P = 0.280). Parathyroid hormone (PTH) in group B exhibited a better recovery tendency. The incidence of postoperative symptomatic hypocalcemia in group B was significantly lower than group A (26.92% vs. 42.42%, P = 0.020). Independent factors predicting protracted hypoparathyroidism included sex, preoperative serum calcium, and POD1 PTH.

CONCLUSION

Calcium and vitamin D supplementation administered exclusively to symptomatic patients achieved the same effect on protracted hypoparathyroidism as routine supplementation. However, routine supplementation significantly reduced postoperative hypocalcemia. Extra attention is necessary in female patients with high preoperative serum calcium and patients with low POD1 PTH.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR), ChiCTR1900022194. Registered March 30, 2019.

Preoperative Vitamin D Deficiency is a Risk Factor for Postthyroidectomy Hypoparathyroidism: A Systematic Review and Meta-Analysis of Observational Studies

CONTEXT

Whether preoperative vitamin D deficiency (VDD) contributes to postoperative hypoparathyroidism (hypoPT) risk is unknown.

OBJECTIVE

This work aimed to meta-analyze the best available evidence regarding the association between preoperative vitamin D status and hypoPT risk.

METHODS

A comprehensive literature search was conducted in PubMed, CENTRAL, and Scopus databases, up to October 31, 2020. Study selection included patients undergoing thyroidectomy with preoperative vitamin D status and postoperative hypoPT data. Two researchers independently extracted data from eligible studies. Data were expressed as risk ratio (RR) with 95% CI. The I2 index was employed for heterogeneity.

RESULTS

Thirty-nine studies were included in the quantitative analysis (61 915 cases with transient and 5712 with permanent hypoPT). Patients with VDD demonstrated a higher risk for transient hypoPT compared with those with preoperative vitamin D sufficiency (RR 1.92, 95% CI, 1.50-2.45, I2 = 85%). These results remained significant for patients with preoperative 25-hydroxyvitamin D concentrations less than or equal to 20 ng/mL (mild VDD; RR 1.46, 95% CI, 1.10-1.94, I2 = 88%) and less than or equal to 10 ng/mL (severe VDD; RR 1.98, 95% CI 1.42-2.76, I2 = 85%). The risk of permanent hypoPT was increased only in cases with severe VDD (RR 2.45, 95% CI, 1.30-4.63, I2 = 45%). No difference was evident in subgroup analysis according to study design or quality.

CONCLUSION

Patients with preoperative VDD are at increased risk of transient hypoPT following thyroidectomy. The risk for permanent hypoPT is increased only for those with severe VDD.