Transient Problems With Calcium Likely Post-surgery if Vitamin D Levels Low, Study Finds

Low vitamin D levels increase the risk of temporary hypocalcemia, or low blood calcium levels, and hypoparathyroidism following surgery to remove the parathyroid glands, a study found.

The study, “Preoperative Vitamin D Levels as a Predictor of Transient Hypocalcemia and Hypoparathyroidism After Parathyroidectomy,” was published in the journal Scientific Reports.

Hypocalcemia commonly occurs after parathyroidectomy, a procedure to remove the parathyroid glands. Patients with primary hyperparathyroidism, which occurs when one or more abnormal parathyroid glands overproduce the parathyroid hormone (PTH), commonly undergo this surgery, as it is more effective and less costly than long-term medical management.

Because nerves, muscles, and bones all need calcium to function properly, common effects of hypocalcemia include tingling, muscle cramps, and bone loss, as well as cognitive issues, such as irritability and memory loss.

Data to help predict and manage hypocalcemia are still lacking. Vitamin D regulates calcium levels and plays a key role in the immune and nervous systems.

Researchers in Turkey reviewed medical records to evaluate how low preoperative vitamin D levels influenced the risk of transient hypocalcemia and hypoparathyroidism, or unusually low levels of PTH, after surgery.

The scientists analyzed the records of 180 patients with primary hyperparathyroidism (PHTH), who underwent either minimally invasive or unilateral parathyroidectomy. Their average age was 54.9, and roughly 82% were women. PHPT is more common among women, especially after menopause.

Before surgery, 22 patients (12.2%) had normal vitamin D levels. By measuring the amount of the vitamin D by-product 25(OH)D, vitamin D deficiency was found in 62.2% and vitamin D insufficiency in 25.6% of these patients. Insufficiency implies a milder decrease in 25(OH)D levels — within 20–30 nanograms (ng)/mL — than vitamin D deficiency (up to 20 ng/mL).

Following surgery, 37% of the patients had transient hypocalcemia, and 24% had transient hypoparathyroidism.

Those with vitamin D deficiency or insufficiency showed low median calcium levels relative to patients with normal vitamin D levels. Transient hypocalcemia, defined as blood calcium levels up to 8.4 mg/dL, and hypoparathyroidism were significantly more common in the vitamin D deficiency and insufficiency groups.

“Vitamin D deficiency is an independent contributor to transient hypocalcemia and hypoparathyroidism following parathyroidectomy,” the scientists wrote.

Theoretically, they said, patients with lower vitamin D are more prone to develop hypocalcemia, due to a higher dependency on PTH to manage the reabsorption of calcium.

PTH mobilizes calcium from the bones, reduces calcium loss via urine, and increases calcium absorption from food in the gut. Without sufficient levels of the parathyroid hormone, as happens during transient hypoparathyroidism, calcium levels remain low.

“To the best of our knowledge, this is the first study in literature to have investigated the relationship between postoperative hypocalcemia and vitamin D after parathyroidectomy,” the researchers added. As such, much remains to be understood, including the link between hypocalcemia with vitamin D following surgery.