PTH Levels in Children Soon After Surgery Show Risk of Hypocalcemia

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by Forest Ray PhD |

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Assessing parathyroid hormone (PTH) levels in children after surgery to remove the thyroid gland, and beginning preventive therapy to those at high risk of hypocalcemia, increased safety and shorted their hospital stay, a study reported.

Hypocalcemia, or potentially harmful low calcium levels, is a frequent complication of surgery to remove the thyroid, known as a thyroidectomy.

The study, “Improving safety in pediatric thyroidectomy by PTH measurements,” was published in the journal Clinical Endocrinology.

Hypocalcemia following a thyroidectomy can cause muscle cramps, pain, weakness, spasms, and confusion. It occurs in an estimated 26% to 63% of pediatric patients following this surgery.

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Although usually temporary, hypocalcemia can lengthen a patient’s hospital stay and require frequent blood samples to monitor calcium levels. When these levels fall, calcium supplements may be given.

Simply treating all patients preventively with calcium supplements, however, is complicated by the risk of hypercalcemia, or too much calcium in the blood. Hypercalcemia can also cause a range of symptoms, including nausea, bone pain, muscle weakness, confusion, and fatigue.

Investigators at the Hospital de Niños Dr. Ricardo Gutiérrez, in Buenos Aires, Argentina, established a cut-off value for PTH that could predict hypocalcemia in hpyoparathyroidism with an estimated 93% sensitivity (rate of true positives) and 100% specificity (rate of true negatives) through two PTH measures, taken five minutes and 60 minutes after thyroid gland removal.

Patients deemed at high risk through this measurement could then be preventively treated for hypocalcemia with calcium and vitamin D supplements, while low-risk patients could undergo 48 hours of calcium-level monitoring, with both patients and parents warned about the symptoms of hypocalcemia.

Based on this cut-off value, the Hospital de Niños team conducted a study to test if their approach could lower the incidence of hypocalcemia and the length of hospital stays for high-risk children and teenagers with hypoparathyroidism. They also investigated the safety of taking fewer blood draws to measure calcium in low-risk patients.

As a control group, the researchers compared their results to records of 32 past cases with equivalent PTH measurements; all patients in this group were treated for hypocalcemia after they began showing symptoms.

The scientists recruited 66 patients (52 females) between the ages of 2 and 19 for their study. These pediatric patients were categorized as high risk if their PTH value at five minutes after surgery (PTH-5) was no more than 1.6 picomol(pmol)/L, or if their PTH-5 was between 1.6 and 2 pmol/L and their PTH at 60 minutes was no more than 1.6 pmol/L.

Based on this cut-off,  30 patients were seen as high risk and started on intravenous (into-the-vein) calcium supplementation immediately after surgery. Five of them (17%) developed hypocalcemia, as did all 14 control group patients predicted to be at high risk.

Calcitriol, a form of vitamin D3, was added to their treatment regimen 24 hours after beginning calcium.

Hospital stays for these patients was a medium of three days, compared with six days among controls.

The 36 low-risk participants had significantly less calcium sampling over a 48-hour post-surgery period relative to the control group. Eight (22%) developed hypocalcemia, and their median hospital stay was six days, similar to that of controls.

All told, hypocalcemia occurred in 20% of the total study group, and 47% of the control group, for a 58% overall decrease in hypocalcemia.

“Starting intravenous [calcium] and calcitriol supplementation before the occurrence of hypocalcemia was probably the intervention that led to shorter hospitalizations” in high-risk pediatric patients, the researchers wrote.

Of the 25 children whose thyroidectomy was due to thyroid cancer, lymph nodes and surrounding neck tissue were also removed, and 21 showed an elevated risk for hypoparathyroidism or hypocalcemia, the researchers noted.

“We consider,” they wrote, “that these patients do not benefit from intra or postoperative PTH determinations, and that the early preventive perioperative [around the time of surgery] management of the hypocalcemia with intravenous [calcium] and calcitriol supplementation” is appropriate.

“Undoubtedly, our strategy improves the postsurgical safety of children and adolescents undergoing thyroidectomy, and it is cost-effective,” the team added.