PSA is the most popular and widely used tumor marker in medicine and plays a prominent role in the diagnosis and treatment of patients with prostate cancer. After PSA was discovered in the 1970s, observations were made that it could be a useful marker for prostate cancer and became a focus for research into the 1980s. Initially, diurnal variation of PSA was investigated in small studies with designs irrelevant to clinical practice.
However, during the last 40 years, thousands of studies have been performed for the relation of serum levels of this molecule with prostate cancer. Diurnal variation of this enzyme has not been remembered and not thoroughly investigated. It is well-known that testosterone has a diurnal rhythm and patients under treatment with medical or surgical castration or 5 alpha-reductase inhibitors have a decline in PSA levels. Therefore, PSA production is observed to be closely related to testosterone. This made us think that PSA may have a diurnal variation with great impact on the diagnosis of patients with prostate cancer.
In clinical practice, there is no advice for the timing of measurement of PSA for the diagnosis of prostate cancer. In our study, we found a decline in PSA levels when measured between the times of 3:00p - 3:30p in approximately 90% of patients with benign prostatic hyperplasia or prostate cancer. This may change the decision of the clinician for prostate biopsy particularly for PSA levels between 3-4 ng/ml or 4-5 ng/ml.1 Timing of measurement of PSA may also influence follow-up of patients with prostate cancer.
Written by: Hakkı Uzun, MD, Department of Urology, Recep Tayyip Erdogan University School of Medicine, Rize, Turkey
1. Uzun, H, Arpa, M. The impact of diurnal variation of PSA on timing of measurement in prostate biopsy. The Prostate. 2019; 79: 1666‐1672. https://doi.org/10.1002/pros.23891