Plasma concentrations of FSH and testosterone in male infertile patients.

We studied the statistical distribution of the plasma concentrations of FSH and testosterone in patients with oligoazoospermia as compared with normospermic subjects. The plasma concentration of FSH was determined in 429 patients with oligoazoospermia and 282 normospermic subjects ("controls"). In 118 out of these 429 patients and in 47 of the 282 controls, the plasma concentration of testosterone was also measured. The plasma concentrations of FSH differed significantly depending on the patients' values of spermatic concentration. The most significant difference was observed between azoospermic patients and controls, whereas the difference between patients with mild oligospermia and controls was not significant. Conversely, the plasma concentrations of testosterone did not correlate with the values of spermatic concentration and even the difference between azoospermic patients and controls did not reach the significance level. In addition, testosterone plasma concentrations did not differ between two sub-groups of patients who were defined depending on whether the plasma concentration of FSH was normal or high. Our findings confirm the inverse relation between plasma FSH levels and spermatic concentration which had already been observed in previous studies. However, a considerable overlap in the plasma concentrations of FSH has been found between sub-groups of patients with different spermatic concentrations. This overlap limits the clinical usefulness of the measurement of FSH concentration inasmuch as normal FSH plasma levels may often be associated with any value of spermatic concentration. Also, our data confirm that the measurement of testosterone plasma levels provides little clinical usefulness in male infertile patients.