Aim: To access beta-endorphin levels in serum as well as seminal plasma in different infertile male groups.

Methods: Beta-endorphin was estimated in the serum and seminal plasma by enzyme-linked immunosorbent assay (ELISA) method in 80 infertile men equally divided into four groups: non-obstructive azoospermia (NOA), obstructive azoospermia (OA), congenital bilateral absent vas deferens (CBVAD) and asthenozoospermia. The results were compared to those of 20 normozoospermic proven fertile men.

Results: There was a decrease in the mean levels of beta-endorphin in the seminal plasma of all successive infertile groups (mean SD: NOA 51.30 27.37, OA 51.88 9.47, CBAVD 20.36 13.39, asthenozoospermia 49.26 12.49 pg/mL, respectively) compared to the normozoospermic fertile control (87.23 29.55 pg/mL). This relation was not present in mean serum level of beta-endorphin between four infertile groups (51.09 14.71, 49.76 12.4, 33.96 7.2, 69.1 16.57 pg/mL, respectively) and the fertile control group (49.26 31.32 pg/mL). The CBVAD group showed the lowest seminal plasma mean level of beta-endorphin. Testicular contribution of seminal beta-endorphin was estimated to be approximately 40%. Seminal beta-endorphin showed significant correlation with the sperm concentration (r = 0.699, P = 0.0188) and nonsignificant correlation with its serum level (r = 0.375, P = 0.185) or with the sperm motility percentage (r = 0.470, P = 0.899).

Conclusion: The estimation of beta-endorphin alone is not conclusive to evaluate male reproduction as there are many other opiates acting at the hypothalamic pituitary gonadal axis.

Keywords: azoospermia, beta-endorphin, male infertility, opioid peptides, semen, seminal plasma

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