Measurement of citric acid in semen is used in the investigation of male infertility as well as in the investigation of prostate function.
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Citric acid is present in all living cells. It is not only an essential intermediate in the tricarboxylic acid cycle (Krebs cycle) but also a key component in the metabolism of fatty acids, cholesterol, and the synthesis of various hormones, the glyoxylic acid cycle, and nitrogen metabolism. Because of this metabolic importance, abnormal citric acid levels have been linked to many diseases.
The prostate's primary function is to store and secrete a clear fluid (pH 7.3). This fluid makes up about 50% of the volume of seminal plasma, which, together with the spermatozoa, constitutes the semen.
Poor semen quality can result from either the production of abnormal spermatozoa from the testicles, damage to the spermatozoa as they travel through the testicles and epididymis, or abnormal secretions from the accessory glands of the genital system. Accessory gland secretions can be measured to assess the function of these glands, e.g., citric acid, zinc, and acid phosphatase for the prostate, fructose, and prostaglandins for the seminal vesicles, L-carnitine, and neutral alpha-glucosidase for the epididymis.
Urogenital tract infections can sometimes decrease the secretion of these markers, but the total measured value may remain within the normal range. An infection can also cause irreversible damage to the secretory epithelium, reducing the secretory capacity even after treatment.
Prostate secretory capacity. The amount of zinc, citric acid, and acid phosphatase in the semen is a reliable measure of the secretory capacity of the prostate.
Recently, citric acid in semen has been used as a marker to distinguish prostate cancer.
