MedWire News: High levels of a hormone occurring normally in the body may be the cause of some men’s raised prostate-specific antigen (PSA) levels, report US researchers.
In addition to indicating possible cancer or infection, a raised PSA level is also significantly associated with elevated levels of serum calcium and parathyroid hormone (PTH), and may not necessarily imply the need for a prostate biopsy, say the researchers.
“Men without prostate cancer who have high levels of serum PTH… may be more likely to receive prostate biopsy than are men with lower levels of serum PTH,” observe Gary Schwartz (Wake Forest University in Winston-Salem, North Carolina, USA ) and Halcyon Skinner (University of Wisconsin, USA).
“This higher rate of biopsy could lead to the increased detection of clinically insignificant prostate cancer (over detection) and to a higher rate of unnecessary treatment,” they suggest.
Previous research has implicated calcium and PTH, which regulates calcium levels in the blood, in the development of prostate cancer, but the current study is the first to show an association with normal prostate tissue.
The researchers examined the total and free PSA levels of 1273 men without prostate cancer from the National Health and Nutrition Survey. They evaluated the association between serum levels of PSA, calcium, and PTH.
The average age of the men was 55.7 years, average total PSA was 1.47 ng/ml, and 10.5% of the cohort were African American.
After adjusting the results for age, race, and obesity – all of which are associated with higher PSA levels – the researchers found that serum levels of PTH and calcium were significantly associated with serum PSA. One standard deviation increase in log-transformed PTH resulted in a 0.9 log unit increase in total PSA.
Men with PTH levels of 66 pg/ml or higher had 43% higher PSA levels, on average, than men with PTH levels at the low end of the normal reference range (10 pg/ml).
Additionally, the researchers found that African–American men were twice as likely to have a PTH level of 66 pg/ml or higher as their Caucasian counterparts (19.2% vs 9.6%).
“It is likely that there are a lot of men out there with elevated PSAs that may be due to elevated PTH rather than prostate cancer,” Schwartz commented.
“If confirmed by other population-based studies, these findings have important implications for the use of PSA as a screening tool for prostate cancer,” the researchers conclude.
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