Parathyroid tissue glows brighter than thyroid cancer under near-infrared light

Surgeons often complain about how difficult it is to leave the parathyroid glands intact while removing thyroid cancer or lymph nodes from the neck, but a recent study suggested a novel way to spot them.

Research published in the Journal of Biomedical Optics found that the parathyroid glands glow under near-infrared light, a luminescence that can be caught using special sensors.

The parathyroid glands are four small bits of tissue hardly larger than grains of rice. Unlike the thyroid, which controls the body's metabolism, hormone production and calcitonin levels, the parathyroid glands exclusively regulate calcium levels. In fact, parathyroid hormone and calcitonin counteract one another.

Accidental removal of these tiny glands can result in hypoparathyroidism, a condition that can result in dry skin, brittle hair and nails, and abdominal pain, according to the National Institutes of Health.

The symptoms of hypothyroidism are quite similar. Therefore, such symptoms generally fall under the label of hypothyroidism for individuals with thyroid cancer who lose parathyroid glands during a thyroidectomy.

In the report, researchers noted that U.S. doctors perform roughly 80,000 endocrine operations each year, a figure expected to rise to 100,000 within a decade. Between 8 and 19 percent of all thyroidectomies damage or remove the parathyroid glands.

Why? Besides being small, these glands are rarely located in the same spot from person to person, often necessitating a microscope to differentiate between thyroid and parathyroid tissue.

The study's authors, who hail from Vanderbilt University, used a technique called Raman spectroscopy, which uses low-powered lasers to deliver near-infrared light and fiber optics to detect how much is reflected off of tissue.

Co-author Lisa White decided to try using lasers to detect the parathyroid glands after reading a study describing a similar technique used to image liver cancer.

Researchers found that their modified method, near-infrared autofluorescence, not only worked but was an astounding success.

"We have taken measurements with more than 50 patients now and we have found this effect 100 percent of the time, even when the tissue is diseased. That is amazing. You almost never get 100 percent results in biological studies," co-author Anita Mahadevan-Jansen noted.

The team reported that the parathyroid glands glow between two and 10 times brighter than any other tissue in the neck when exposed to near-infrared light, though no one is currently sure why.

They concluded that such a detection strategy may help doctors preserve parathyroid tissue when removing thyroid cancer.