OBJECTIVESTo investigate the possible differences in the inhibin B levels of seminal plasma and serum between fertile and infertile males and to obtain information on the relation between serum inhibin B or seminal plasma inhibin B and spermatogenesis.

METHODSSemen and blood samples were collected from fertile(n = 20), oligospermia(n = 20), asthenospermia(n = 22) and non-obstructive azoospermia(NOA) (n = 20) males at 8:00 am = 10:00 am. Semen parameters were analyzed. Levels of inhibin B in seminal plasma and serum, ACP, Fru, alpha-Glu in seminal plasma, serum levels of FSH, T, LH were determined.

RESULTSBoth levels of serum inhibin B and levels of seminal plasma inhibin B correlated significantly negatively with serum FSH(r = -0.536, P < 0.001 vs r = -0.288, P = 0.01), and statistically positively with sperm concentration(r = 0.49, P < 0.001 vs r = 0.48, P < 0.001). There was positive correlation between levels of seminal plasma inhibin B and activity of alpha-Glu in seminal plasma (r = 0.377, P = 0.001). The difference in levels of seminal plasma inhibin B was found only between fertile males or asthenospermia and NOA (P < 0.01 and P < 0.05, respectively). However, significant differences in levels of serum inhibin B were found not only between males with normal sperm concentration (including fertile males and asthenospermia) and NOA (P < 0.01), fertile males and oligospermia (P < 0.05), but also between oligospermia and NOA (P < 0.05). There was no correlation between serum inhibin B and seminal plasma inhibin B.

CONCLUSIONSBoth levels of serum inhibin B and seminal plasma inhibin B could reflect testis spermatogenesis status. Levels of seminal plasma inhibin B could also reflect the function of seminiferous duct, but the wide range of values limited its applicability.