# Paradoxical Elevation of Parathyroid Hormone Levels following Preoperative Native Vitamin D Supplementation in a Patient with Graves’ Disease Undergoing Total Thyroidectomy: A Case Report

## TL;DR

A patient with Graves' disease experienced unexpected high parathyroid hormone levels after vitamin D supplementation before thyroid surgery.

## Contribution

This is the first report of paradoxical PTH elevation following preoperative vitamin D supplementation in a Graves’ disease patient.

## Key findings

- Preoperative vitamin D supplementation led to increased PTH and bone formation markers.
- FGF23 levels remained unchanged despite elevated PTH and 1,25-dihydroxyvitamin D.
- The patient developed transient hypoparathyroidism after surgery.

## Abstract

Hypocalcemia is a common complication after total thyroidectomy, particularly in patients with Graves’ disease and high bone turnover. Preoperative vitamin D deficiency is a known risk factor for postoperative hypocalcemia; however, the effects of vitamin D supplementation remain controversial. This is the first study to document a paradoxical increase in parathyroid hormone (PTH) levels after preoperative vitamin D supplementation in a patient undergoing total thyroidectomy.

We report the case of a 68-year-old woman with Graves’ disease and coexisting thyroid cancer who received native vitamin D (2000 IU/day) for 4 weeks before surgery. This unexpectedly resulted in a marked increase in PTH levels and bone formation markers, suggesting the worsening of secondary hyperparathyroidism. Interestingly, fibroblast growth factor 23 levels remained unchanged despite an increase in PTH and 1,25-dihydroxyvitamin D levels. Postoperatively, she developed transient hypoparathyroidism.

Native vitamin D supplementation may, paradoxically, worsen secondary hyperparathyroidism in some patients, highlighting the need for careful preoperative metabolic assessment and individualized management strategies.