Persistently Low iPTH Not Good for Hemodialysis Patients

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Persistently low levels of intact parathyroid hormone (iPTH) are independently associated with progression of aortic arch calcification (AAC) and death among incident hemodialysis (HD) patients, according to a new study.

The study of 94 HD patients by Sang Heon Song, MD, PhD, of Pusan National University Hospital in Busan, Republic of Korea, and colleagues found that persistently low iPTH (below 150 pg/mL) was associated with a significant fivefold increased risk of AAC progression and a significant eightfold increased risk of death compared with patients who had optimal iPTH levels (between 150 and 300 pg/mL). AAC at baseline was associated with a significant threefold increased risk of AAC progression, the researchers reported in Clinical and Experimental Nephrology (published online ahead of print).

Within the persistently low iPTH group, patients with iPTH levels below 60 pg/mL had significantly lower serum phosphate, albumin, and total cholesterol, as well as significantly greater ACC progression and mortality, compared with patients who had iPTH levels between 60 and 150 mg/mL.

The study population was enrolled from January 2004 to December 2008. All patients had iPTH levels below 300 pg/mL during their first year on dialysis. For the study, the investigators scored AAC using posterior-anterior plain chest X-rays. They determined baseline AAC score within three months before and after HD initiation. The median follow-up period was 46.9 months.

Previous studies have demonstrated that vascular calcification is closely related to cardiovascular and all-cause mortality, the researchers pointed out. Their study, however, did not find a significant association between AAC progression and death, and they believe this might be due to the relatively shorter follow-up period and small sample size, according to the report.

The authors stated that there are two possible explanations for increased mortality in patients with persistently low iPTH. One is that persistent uremic hypoparathyroidism may be associated indirectly with mortality by its association with prolonged malnutrition. The other explanation is that uremic hypoparathyroidism is associated with vascular calcification.

Based on their findings, the researchers suggest that nephrologists “should carefully control mineral metabolism in patients with positive AAC seen on plain X-rays at the time of the first hemodialysis.”

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