Human chorionic gonadotropin (hCG) in the male reproductive tract

Normal hypothalamic-pituitary testicular and prostatic functions are essential for maintenance of male fertility, whereby glycoprotein hormones (GPH) as well as androgens are major endocrine and local regulators. We have investigated whether the GPH human chorionic gonadotropin (hCG) and the free alpha and beta subunits thereof are produced in the target organs themselves and potentially act as auto/paracrine modulators of fertility. Immunofluorometric assays (IFMAs) based on our panel of highly selective monoclonal antibodies, immunohistochemistry (IHC), confocal laser scanning microscopy (CLSM) and 1- and 2D gel electrophoreses with subsequent western blotting have been utilized for the detection of hCGα, hCGβ and its metabolite hCGβ core fragment (cf) in human testis, prostate and seminal plasma. Both organs synthesize hCGα and hCGβ, which are subsequently detectable at high concentrations in seminal plasma of healthy probands (n = 17): hCGα 2630 ± 520 ng/mL (mean ± S.E.M.), hCGβ 2 ± 0.28 ng/mL, hCGβcf and hCG 0.19 ± 0.039 ng/mL. These parameters significantly exceed physiological values, e.g. ten thousand-fold in the case of hCGα, in serum of young men (n = 20): hCGα 0.142 ± 0.054 ng/mL (mean ± S.E.M.), hCGβ 0.05 ng/mL and hCG 0.004 ± 0.003 ng/mL. Levels of these markers were not correlated with sperm counts. Of all body fluids including those of pregnant women seminal plasma is the richest physiological source for genuine free i.e. non-dissociated GPHα (Mr,app 23 k) which may even appear as di- or tetramers. Its concentration is similar to that observed in maternal serum (weeks 10-12 of gestation) and in extra-embryonic coelomic fluid. In contrast to those fluids where ratios of free subunits to hCG are in the range of 1:100 highly inverse ratios in the range of 10.000:1.000:1 were observed for hCGα:hCGβ:hCG in seminal plasma. hCGα is not derived from heterodimeric GPH suggesting hCG-independent functions of hCGα and hCGβ in male and female fertility.