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Myth: Because women lack prostate glands, they do not have a prostate-specific antigen (PSA) level that can be assessed with a serum blood sample (see Figure 1).
Answer: PSA is a serine protease expressed in high levels in prostate epithelium, and elevated serum PSA has been a well-established marker for prostate cancer since 1980 (Black & Diamandis, 2000). PSA is a useful laboratory diagnostic tool; as PSA level rises, the risk for prostate cancer increases. In men with cancer, PSA level is used to monitor the effectiveness of cancer therapy and as surveillance for recurrence and advancing disease. However, this column will discuss research that has challenged the belief that PSA is restricted to the prostate gland.
PSA is measured in two forms. The free PSA test measures the percentage that is not bound to proteins in the blood; in men with prostate cancer, the ratio of free to typical PSA is reduced (Hoffman, 2009). The typical PSA test also is known as the total PSA test. In a healthy man, total PSA is 1 ng/ml or less (8.8% risk for prostate cancer); however, the risk rises to 58.2% when the PSA level is higher than 10 ng/ml (Cleveland Clinic Pathology and Medicine Laboratory Institute, 2009). In a healthy woman, serum PSA concentration is less than 0.0004 ng/ml (Black et al., 2000).
Although its physiologic function in women has not been determined, PSA has been found in the periurethral gland, normal and hyperplastic breast tissue, breast tumors and cysts, breast secretions (e.g., nipple aspirate fluid), the milk of lactating women, breast cystic fluid, the placenta, and amniotic fluid. PSA also has been found in cancerous and healthy ovarian, endometrial, adrenal, skin, lung, colon, liver, kidney, and salivary tissue (Black & Diamandis, 2000; Black et al., 2000; Kocak, Tarcan, Beydilli, Koc, & Haberal, 2004). As in men, PSA in women is affected by hormones; therefore, PSA levels fluctuate during a woman's menstrual cycle (Aksoy, Akcay, Umudum, Yildirim, & Memisogull-ari, 2002; Galadari, Al-Mazroei, & Alkaabi, 2004). PSA levels peak in the mid- to late-follicular phase of a woman's cycle and are higher in pregnant women than in healthy nonpregnant women (Aksoy et al.). A 2002 study found that the PSA level detected in a woman's saliva equaled...