Newly identified parathormone-secreting cells in the thyroid tissue

After total parathyroidectomy, circulating parathyroid hormone (PTH) levels typically do not fall to zero, and the biological source of this residual secretion remains unclear.

Patients were divided into three groups. Group 1 (n = 46) comprised total thyroidectomy tissues; Group 2 (n = 46) included non-thyroid/non-parathyroid tissues (negative controls); and Group 3 (n = 7) consisted of healthy parathyroid gland tissues (positive controls). All tissues were kept in physiological saline immediately after resection for 30 min, and then 2 mL samples were taken to measure PTH concentrations. In addition, confocal immunofluorescence staining was performed on all specimens.

Mean PTH levels were 38.50 ± 7.92 pg/mL in Group 1, 6.95 ± 1.22 pg/mL in Group 2, and 648.00 ± 15.82 pg/mL in Group 3 (p = 0.01). Confocal microscopy after immunofluorescence staining revealed cells with PTH-positive granules in the thyroid tissue that were morphologically similar to thyroid epithelial cells.

Thyroid tissues secrete a significant amount of PTH compared to many other tissues. This may be due to a new cell population identified by immunofluorescence staining.