Measuring the levels of parathyroid hormone and blood calcium levels 24 hours after a total thyroidectomy (the surgical removal of the entire thyroid gland) can predict which patients may develop permanent hypoparathyroidism, according to researchers from China.
Their study, “Prediction of permanent hypoparathyroidism by parathyroid hormone and serum calcium 24 h after thyroidectomy,” was published in the American Journal of Otolaryngology.
Thyroid cancer is a common tumor of the endocrine system. A total thyroidectomy is one of the most frequently used methods to treat the disease.
One of the post-surgical complications after total thyroidectomy is hypoparathyroidism, a condition characterized by low levels of the parathyroid hormone.
Because the parathyroid hormone regulates blood calcium levels, permanent hypoparathyroidism (pHPP) can cause hypocalcemia (low levels of calcium), leading to physical and mental disorders.
However, no consensus exists about the factor most critical to predict which patients may develop postoperative pHPP. And the correlation between the levels of parathyroid hormone and serum calcium after a total thyroidectomy is still not completely understood.
Researchers collected and retrospectively analyzed clinical data from 110 patients who underwent total thyroidectomy at Xiangya Hospital in China from September 2014 to July 2015.
Patients were divided into three groups — normal parathyroid function after total thyroidectomy (42 patients); temporary hypoparathyroidism (58 patients); and permanent hypoparathyroidism (10 patients).
Before the surgery, intact parathyroid hormone (iPTH) and serum calcium levels in patients across all three groups was not significantly different.
At 24 hours after surgery patients in the permanent hypoparathyroidism group had statistically significantly lower levels of iPTH, and, to a lower extent, serum calcium levels.
Average iPTH levels (24 hours post-surgery) were 24.36 pg/mL in the normal parathyroid function group; 7.43 pg/mL in the temporary hypoparathyroidism group; and 1.12 pg/mL in the permanent hypoparathyroidism group.
Average blood serum calcium levels were 2.16 mmol/L, 2.06 mmol/L, and 1.87 mmol/L in the same groups, respectively.
Using statistical analyses, researchers determined that using an iPTH cutoff value at 24 hours post-surgery of less than or equal to 3.14 pg/mL may help predict which patients will develop permanent hypoparathyroidism. This cutoff value was extremely sensitive and specific.
Researchers also determined that the cutoff value for blood calcium levels should be equal to or lower than 2.03 mmol/L to predict permanent hypoparathyroidism development at 24 hours post-surgery.
“Measurement of the postoperative 24-hour intact parathyroid hormone and serum calcium concentration can predict the occurrence of permanent hypoparathyroidism and the former is more advantageous,” researchers wrote.
“This will facilitate early detection and diagnosis, thus avoiding the pain of repeated blood tests and the associated economic burden,” they added.
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