The role of the male factors in the couple's infertility has been significantly increased in recent years due to a sententious assessment of male reproductive functions and enhanced diagnostic tools. We investigated the correlations among the seminal plasma (SP) levels of each of zinc, testis-expressed sequence 101 (TEX101), and free amino acids levels with reproductive hormones in adult fertile and infertile men. The study included 100 infertile men categorized into 50 non-obstructive azoospermic patients and 50 patients with idiopathic oligoasthenoteratozoospermia (iOAT), in addition to 50 fertile controls. Semen analyses, serum ELISA assays for male reproductive hormones (follicle-stimulating hormone (FSH), luteinizing hormone (LH), total testosterone, and prolactin), colorimetric assays of SP zinc and total proteins, SP free amino acids using high-performance liquid chromatography (HPLC), and ELISA assays of SP TEX101 were performed for all subjects. Infertile men with azoospermia had significantly lower SP median levels of zinc, TEX101, and many SP free amino acids compared to both men with iOAT and fertile controls (P ˂ 0.05 for all). There were lower SP levels of zinc and some free amino acids among men with iOAT compared to the fertile controls (P ˂ 0.05 for all) with non-significant difference regarding to SP TEX101 (P ˃ 0.05). Azoospermic men exhibited negative correlations between FSH, LH, and prolactin with some SP free amino acids (P ˂ 0.05 for all), and a positive correlation between glycine with total testosterone (P ˂ 0.05). Among iOAT patients, LH and FSH were positively correlated with SP zinc, TEX101, and some measured free amino acids (P ˂ 0.05 for all). Total testosterone was positively correlated with some amino acids, while prolactin was negatively correlated with glycine (P ˂ 0.05 for all). iOAT and azoospermic men exhibited low SP zinc and some free amino acids levels that were more pronounced in azoospermic men and were significantly associated with the reproductive hormones. TEX101 could be a helpful confirmatory test for azoospermia.
Keywords: Amino acids; Male infertility; Seminal plasma; TEX101; Zinc.