Intensely treating hyperphosphatemia helps reduce intact parathyroid hormone (iPTH) levels in hemodialysis (HD) patients, new study findings suggest.

Of 95 HD patients with more than 1.78 mmol/L serum phosphorus and 300 pg/dL iPTH, 43 agreed to intensive treatment and 52 did not. Treated patients received phosphate binders (lanthanum carbonate, sevelamer, and/or calcium agents) along with dietary phosphate restriction and intensified HD. Control patients received low doses of calcium agents only when serum calcium level fell below 2.54 mmol/L. No one received vitamin D sterol therapy (such as calcitriol or paricalcitol) or calcimimetics. The total observation period was 6 months.

In the treatment group, mean serum phosphorus declined significantly from 2.66 mmol/L at baseline to 2.02 mmol/L at 6 months. In the control group, it rose significantly from 2.29 to 2.74 mmol/L. In the intensive treatment group, iPTH fell from 741.81 to 638.93 pg/dL, whereas it increased from 557.28 to 871.05 pg/dL in the control group, Tian-Jun Guan, MD, and colleagues from Xiamen University in China reported in Renal Failure (2018;40:15-21).

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The investigators categorized patients in the intensive treatment arm as rapid or slow responders based on who achieved a greater than 20% reduction in serum phosphorus in the first 2 months. In rapid responders (20% reduction in 2 months or less), iPTH dropped a significant 16.93% from baseline, but it increased 0.68% in slow responders (20% reduction after 2 months). The team speculated that secondary hyperparathyroidism (SHPT) worsened over time in slow responders.

“Our findings indicate that reduction in high serum phosphorus would help to decrease iPTH levels in patients on maintenance hemodialysis, especially for those rapid responders who achieved a substantial reduction in serum phosphorus within 2 months,” Dr Guan and collaborators stated.

The mechanisms linking serum phosphorus with SHPT are still unclear. The authors suggested that serum phosphorus might regulate the expression of the calcium-sensing receptor in the parathyroid glands. Dietary phosphate might also play a role in PTH regulation, they noted.

Among the study’s limitations, information on patients’ dietary habits was lacking. The investigators also pointed out that wealthier patients likely opted for treatment because phosphate binders are not widely covered by insurance in China.

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Chen L, He JX, Chen YY, Ling YS, Lin CH, and Guan TJ. Intensified treatment of hyperphosphatemia associated with reduction in parathyroid hormone in patients on maintenance hemodialysis. Ren Fail. 2018;40:15-21.  DOI:10.1080/0886022X.2017.1419966