A study on pruritus after parathyroidectomy for secondary hyperparathyroidism

Background: The effective therapy for uremic pruritus remains a clinical challenge, and the factors affecting the pruritus before and after parathyroidectomy have not been defined. Study Design: Thirty-seven patients were operated on for secondary hyperparathyroidism. Their ages ranged from 14 to 73 years, and the duration of dialysis from 12 to as long as 168 months. Indications for surgery were skin itch in 22 patients and other reasons in 15 patients. Serum levels of calcium, phosphorus, intact PTH (i-PTH), and alkaline phosphatase were checked at two different intervals before surgery and I week after operation. Immunohistochemical stain of mast cells, antihuman macrophage (CD68), antihuman dendritic reticulum cell (CD35), and i-PTH (IHPTH) were performed on skin specimens. Skin samples were prepared into tissue homogenates and analyzed for concentrations of interleukin-2 (Il- 2) and tumor necrosis factor-α (TNF-α). Il-2 and TNF-α were measured by sandwich enzyme-linked immunosorbent assay. The extent of pruritus was evaluated on a visual analog scale (VAS) ranging from 0 to 10 and a behavior rating scale (BRS) ranging from 0 to 5, at a preoperative stage and 1 week after operation. Results: Serum levels of calcium, phosphorus, the product of calcium and phosphorous (Ca x P), alkaline phosphatase, and i-PTH changed significantly after parathyroidectomy. The VAS decreased from 5.4 ± 3.2 to 1.8 ± 1.5 (p < 0.001). Significant improvement of BRS was achieved 1 week after surgery (p < 0.001), and in the followup period. Before surgery, there was no correlation between serum levels of calcium, phosphorus, Ca x P, alkaline phosphatase, i-PTH, number of mast cells, CD68, CD35, and IHPTH, and the scale of itch estimated with either VAS or BRS. The tissue levels of Il-2 and TNF-α were not detectable in any of them. We noted that high levels of phosphorus and Ca x P affected the postoperative extent of pruritus. But a linear regression test showed Ca x P was the only factor affecting postoperative itch. Conclusions: Pruritus in patients with secondary hyperparathyroidism can be reduced by parathyroidectomy. Apparently, high- level Ca x P is the only factor that seems to affect the postoperative extent of pruritus.