No abstract

Gonadotropin-releasing hormone (GnRH) plays a pivotal role in the physiology of reproduction in mammals. GnRH acts by binding to the GnRH receptor (GnRHR). In humans, only 1 conventional GnRH receptor subtype (type I GnRH receptor) has been found. In the human genome, 2 forms of GnRH have been identified, GnRH-I (mammal GnRH) and GnRH-II (chicken GnRH II). Both forms and their common receptor are expressed, apart from the hypothalamus, in various compartments of the human ovary. Gonadal steroids, gonadotropins, and GnRH itself controls the regulation of the GnRH/GnRHR system gene expression in the human ovary. The 2 types of GnRH acting paracrinally/autocrinally influence ovarian steroidogenesis, decrease the proliferation, and induce apoptosis of ovarian cells. In this review, the biology of GnRH/GnRHR system in humans, the potential roles of GnRH, and the direct effects of GnRH analogues in ovarian cells are discussed.

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During the last decade, studies provided evidence on the indirect or direct participation of leptin in human reproductive functions. Leptin plays a role in puberty, gonadal function, early embryogenesis and fat metabolism during pregnancy [5][6][7]. Mean circulating leptin levels are higher in women compared to men [5][6][7]. At the same time, circulating leptin levels vary during the physiological spontaneous menstrual cycle presenting with lower values during the follicular and higher values during the luteal phase [8][9][10][11][12][13]. This fact supports the notion that leptin plays an important role in female reproductive functions and it fuels questions whether leptin levels are associated with gonadotropin or ovarian steroid levels. These questions still remain open.The participation of leptin in human female reproductive functions raises the question whether other adipokines are related to these functions, too. The present study was designed to investigate the serum levels of Byron AsiMAkopouLos*, AthAnAsios MiLousis*, theodorA GiokA**, GeorGiA kABouRoMiTi**, GeorGe GiAnissLis*, Androniki TRoussA*, MArA siMopouLou*, siMoni kATeRGARi*, GreGory TRipsiAnis*, nikos nikoLeTTos*** Abstract. This study investigated the serum levels of resistin, adiponectin and leptin during the physiological menstrual cycle. sixteen women (age: 19-30 years; body mass index: 19.46-24.9) with regular menstrual cycles participated. Fasting blood samples were collected on alternate days throughout a full menstrual cycle. Mean resistin concentrations were slightly higher during the luteal phase (5.30±0.23 ng/ml) compared to the follicular (4.68±0.07 ng/ml) and midcycle (4.86±0.09 ng/ml) phases (p=0.032). Mean leptin concentrations during the follicular phase (18.14±0.28 ng/ml) were significantly lower compared to the midcycle (21.79±0.29 ng/ml, p=0.006) and luteal phases (23.75±0.64 ng/ml, p<0.001). The variation of adiponectin concentrations throughout the menstrual cycle was not significant. According to the results, circulating resistin, likewise leptin concentrations vary significantly during the physiological menstrual cycle presenting with higher values during the luteal phase. This pattern, although its physiological importance is not clear, suggests that resistin, likewise to leptin, may have a role in the regulation of cyclic female reproductive functions. The stable adiponectin concentrations throughout the menstrual cycle indicate that this adipokine probably does not play a considerable role in female reproductive functions.

Due to the limitations of conventional semen analysis in predicting a man's fertility potential, sperm DNA fragmentation was recently introduced as a novel marker of sperm quality. This prospective study was undertaken to investigate the associations between conventional seminal parameters and DNA fragmentation in Greek men. A total of 669 subject data were evaluated in two groups, normozoospermic (n = 184) and non-normozoospermic (n = 485), according to the WHO 2010 (WHO Laboratory Manual for the Examination and Processing of Human Semen, 5th edn. World Health Organization), reference limits. For all the subjects, semen volume, sperm concentration, total count, rapid and total progressive motility and morphology were recorded following the WHO 2010 methods and DNA fragmentation was assessed by the sperm chromatin dispersion assay. An inverse correlation was established between DNA fragmentation and all conventional seminal parameters except semen volume in men with seminal profiles below the reference limits, with statistical significance for rapid and total progressive motility. Normozoospermic men exhibited lower levels of DNA fragmentation than their non-normozoospermic counterparts, even though the values were not always below 30%. DNA fragmentation testing and traditional semen analysis should therefore be considered as complementary diagnostic tools in a comprehensive evaluation of male infertility.