Sperm plasma membrane ion transporters and male fertility potential: A perspective under the prism of cryopreservation.

Intracellular calcium homeostasis plays a crucial role in spermatozoa by regulating physiological functions associated with sperm quality and male fertility potential. Intracellular calcium fine balance in the sperm cytoplasm is strictly dependent on sperm surface channels including the CatSper channel. CatSpers' role is to ensure the influx of extracellular calcium, while intracellular pH alkalinization serves as a stimulus for the activation of several channels, including CatSper. Overall, the generation of intracellular calcium spikes through CatSper is essential for fertilization-related processes, such as sperm hyperactivation, acrosome reaction, egg chemotaxis, and zona pellucida penetration. Multiple lines of evidence suggest that disruption in the close interaction among ions, pH, and CatSper could impair male fertility potential. In contemporary times, the growing reliance on Medically Assisted Reproduction procedures underscores the impact of cryopreservation on gametes. In fact, a large body of literature raises concerns about the cryo-damages provoked by the freeze-thawing processes, that can affect the plasma membrane integrity, thus the structure of pivotal ion channels, and the fine regulation of both intracellular calcium and pH. This review aims to provide an overview of the importance of the CatSper channel in sperm quality and further fertilization potential. Additionally, it addresses the emerging issue of cryopreservation's impact on the functionality of this sperm channel.

Exogenous progesterone for LH surge prevention is redundant in ovarian stimulation protocols.

During ovarian stimulation for IVF-embryo transfer treatment, a premature LH surge may lead to progesterone elevation that disrupts endometrial maturation and affects the probability of pregnancy following fresh embryo transfer. Preventing this LH surge and progesterone elevation using gonadotrophin-releasing hormone (GnRH) analogues is considered a standard practice. The same policy applies to cycles in which the 'freeze-all' protocol has been selected from the outset (e.g. donors), but the need for this has not been discussed. Moreover, in 'freeze-all' cycles, exogenous progesterone administration tends to replace GnRH antagonists, without reducing efficacy after embryo transfer in frozen-thawed cycles. Nevertheless, as exogenous progesterone is expected to have the same impact on the endometrium as endogenous progesterone, it is clear that, unlike in fresh cycles, in 'freeze-all' cycles an endogenous LH surge prevention does not seem necessary. Therefore, both GnRH antagonists and exogenous progesterone appear to be redundant in 'freeze-all' cycles, and in this context the indications for the use of GnRH analogues in ovarian stimulation protocols need to be revisited.

The Impact of SARS-CoV-2 on Sperm Cryostorage, Theoretical or Real Risk?

Cryopreservation of human gametes and embryos as well as human reproductive tissues has been characterized as an essential process and aspect of assisted reproductive technology (ART). Notably, sperm cryopreservation is a fundamental aspect of cryopreservation in oncological patients or patients undergoing gonadotoxic treatment. Given that there is a risk of contamination or cross-contamination, either theoretical or real, during the procedures of cryopreservation and cryostorage, both the European Society for Human Reproduction and Embryology (ESHRE) and the American Society for Reproductive Medicine (ASRM) have provided updated guidelines for preventing or reducing the contamination risk of sexually transmitted viruses. Given the ongoing and worldwide COVID-19 pandemic, there is considerable interest in what measures should be taken to mitigate SARS-CoV-2 contamination during cryopreservation and cryostorage of semen samples. The SARS-CoV-2 virus is the virus that causes COVID-19, and whose transmission and infection is mainly aerosol-mediated. Several ART professional societies, including ESHRE and ASRM have proposed measures to mitigate the spread of the SARS-CoV-2 virus. Whether the proposed safety directives are enough to mitigate the possible SARS-CoV-2-contamination of sperm samples during cryopreservation or whether the policies should be re-evaluated will be discussed in this review. Additionally, insights regarding the possible impact of COVID-19 vaccination on the safety of sperm cryopreservation will be discussed.

COVID-19 and fertility: a virtual reality.

The COVID-19 pandemic is an extraordinary global situation, and all countries have adopted their own strategies to diminish and eliminate the spread of the virus. All measures are in line with the recommendations provided by the World Health Organization. Scientific societies, such as the European Society for Human Reproduction and Embryology and American Society for Reproductive Medicine, have provided recommendations and guidance to overcome and flatten the growing curve of infection in patients who undergo IVF treatments. Although there is as yet no evidence that the virus causing COVID-19 might have negative effects on IVF outcomes, fertility treatments have been postponed in order to support healthcare systems by avoiding placing them under additional stress. The possibility of the virus affecting sperm function and egg performance cannot be excluded. In addition, an indirect effect of the virus on gametes and embryos during their manipulation cannot be ruled out. This commentary aims to provide some ideas on the possible effect of the virus on gametes and embryos, as well as how it could affect the normal functioning of the embryology laboratory.

The effect of a GnRH antagonist on follicle maturation in normal women.

RESEARCH QUESTION: Ganirelix is a gonadotrophin-releasing hormone (GnRH) antagonist used for the prevention of premature LH surge during ovarian stimulation. What is the impact of ganirelix on follicle maturation in normal women? DESIGN: Ten normally cycling women were investigated during two menstrual cycles, i.e. cycle 1 (control) and cycle 2 (ganirelix). During both cycles, daily blood samples were taken from day 2, while transvaginal ultrasound scans were performed on cycle days 8 and 10 and daily thereafter. During cycle 2, all women were given 0.25 mg/day subcutaneous injections of the GnRH antagonist ganirelix from day 2 until the day of the endogenous LH surge onset in cycle 1. RESULTS: During treatment with ganirelix, serum FSH and oestradiol concentrations remained stable, while those of LH decreased significantly on days 3, 4, 7 and 9 (P < 0.05) compared with controls. Nevertheless, there was no significant within-cycle variation in LH concentrations. From day 10 onwards, no follicle maturation was observed in cycle 2, in contrast to cycle 1. Ovulation occurred in 9 of 10 women in cycle 1. In cycle 2, ovulation was delayed by at least 1 week in eight women. Follicle growth and ovulation occurred in only one woman while on ganirelix treatment. CONCLUSIONS: This study demonstrates for the first time that in normal women dominant follicle selection failed during treatment with ganirelix. As there was a similar gonadotrophin profile in the two cycles, it is suggested that ganirelix interferes with the process of follicle selection by acting in the ovary.

The Effect of Metformin on the Endometrium of Women with Polycystic Ovary Syndrome.

OBJECTIVES: To investigate the effect of metformin on endometrial receptivity in women with polycystic ovary syndrome (PCOS). METHODS: Twenty volunteer women with polycystic ovaries and oligomenorrhea were prospectively investigated. All women were treated with exogenous estradiol and progesterone to simulate a normal menstrual cycle (28-day duration) after GnRH-induced pituitary desensitization. Ten of the women received no other medication (group A, control), while the remaining 10 received metformin (group B, metformin). Endometrial biopsy was performed in all women on day 21 of the 2 simulated cycles. RESULTS: The expression of corticotropin - releasing hormone and urocortin in the endometrium was investigated. There was no significant difference between the 2 groups. A 3-day delay in the secretory maturation of the glandular epithelium relatively to the stroma was observed in 7 out of 10 women of group B (70%) as compared to only 1 out of 10 women of group A (10%, p = 0.02). CONCLUSIONS: It is shown for the first time that metformin administration to women with PCOS did not affect the expression of endometrial receptivity markers but delayed histological glandular maturation. It is suggested that metformin may have an impact on the function of the endometrium in PCOS.

Human Papilloma Virus (HPV) and Fertilization: A Mini Review.

Human papilloma virus (HPV) is one of the most prevalent viral sexually transmitted diseases. The ability of HPV to induce malignancy in the anogenital tract and stomato-pharyngeal cavity is well documented. Moreover, HPV infection may also affect reproductive health and fertility. Although, the impact of HPV on female fertility has not been thoroughly studied it has been found also to have an impact on semen parameters. Relative information can be obtained from studies investigating the relationship between HPV and pregnancy success. Furthermore, there is an ongoing debate whether HPV alters the efficacy of assisted reproductive technologies. An association between HPV and assisted reproductive technologies (ART) programs has been reported. Nevertheless, due to conflicting data and the small number of existing studies further research is required. It remains to be clarified whether HPV detection and genotyping could be included in the diagnostic procedures in couples undergoing in vitro fertilization (IVF)/intrauterine insemination (IUI) treatments. Vaccination of both genders against HPV can reduce the prevalence of HPV infection and eliminate its implications on human fertility. The aim of the present mini-review is to reiterate the association between HPV and human fertility through a systematic literature review.

Submaximal doses of ghrelin do not inhibit gonadotrophin levels but stimulate prolactin secretion in postmenopausal women.

OBJECTIVE: An inhibitory effect of ghrelin on gonadotrophin secretion has been reported in normally menstruating women possibly modulated by endogenous oestrogen. The aim of this study was to examine the effect of ghrelin on gonadotrophin and prolactin (PRL) secretion in oestrogen-deprived postmenopausal women. DESIGN: Prospective intervention study. PATIENTS AND MEASUREMENTS: Ten healthy postmenopausal volunteer women were studied during two 15-days periods of oestrogen treatment (A and B) a month apart. Four experiments (Exp) were performed in total, two on day 1 (Exp 1A and Exp 1B) and two on day 15 (Exp 15A and Exp 15B) of the two periods. The women received in Exp 1A and in Exp 15A two iv injections of ghrelin (0.15 µg/kg at time 0 minute and 0.30 µg/kg at time 90 minutes) and in Exp1B and in Exp 15B normal saline (2 mL), respectively. Blood samples were taken at -15, 0, 30, 60, 90, 120, 150 and 180 minutes. RESULTS: After oestrogen treatment, late follicular phase serum oestradiol levels were attained on day 15 of periods A and B. Ghrelin administration did not affect serum levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), whereas it increased significantly those of growth hormone (GH) and PRL. In Exp 15A, serum PRL increment in response to ghrelin (area under the curve, net increment) was significantly greater than in Exp 1A (P<.05). CONCLUSIONS: This study demonstrates for the first time that in oestrogen-deprived postmenopausal women, ghrelin administration affects neither FSH nor LH levels but stimulates PRL secretion, that is amplified by exogenous oestrogen administration.

Embryological Results of Couples Undergoing ICSI-ET Treatments with Males Carrying the Single Nucleotide Polymorphism rs175080 of the MLH3 Gene.

Human MLH3 (hMLH3) gene has been suggested to play a role in the DNA mismatch repair mechanism, while it may also be associated with abnormal spermatogenesis and subsequently male infertility. The aim of the present study was to investigate possible relationships between the single nucleotide polymorphism (SNP) rs175080 in the MLH3 gene of males and the embryological results in couples undergoing intracytoplasmatic sperm injection-embryo transfer (ICSI-ET) treatments. A total of 132 men volunteered for the study and gave written informed consent. All couples were subjected to ICSI-ET treatments in the years 2010 to 2012. The couples were divided into three groups according to the genotype of their husbands: the wild type GG (n = 28), the heterozygotic type GA (n = 72) and the mutant type AA (n = 32). Significantly lower sperm concentration and progressive motility were observed in the AA group as compared to the other two groups (Concentration: 14.57 ± 4.9 mil/mL in AA, 38.3 ± 5.4 mil/mL in GA and 41.03 ± 6.8 mil/mL in GG, p < 0.05, mean ± standard error of the mean-SEM). However, significantly better embryological results (mean score of embryo quality-MSEQ) were found in the AA (8.12 ± 0.5) and the GA group (7.36 ± 0.4) as compared to the GG group (5.82 ± 0.7), (p < 0.05). Clinical pregnancy rate was significantly higher in the AA genotype group (43.8%) and the GA group (30.6%) than in the GG group (14.3%), (p < 0.05). Live birth rate was not different. It is suggested for the first time that the deteriorating effect of the mutant type on sperm characteristics does not impact on embryo development after fertilization in vitro.

Sperm contributions to oocyte activation: more that meets the eye.

It is well known that for successful fertilization, oocyte activation is required, which involves a signal transduction cascade leading to the conversion of the oocyte to a diploid embryo. During oocyte activation, intracellular calcium levels oscillate repetitively causing exocytosis of cortical granules, the enzymes which the latter contain are released into the perivitelline space, leading to modifications of the zona pellucida (ZP), which prevent the penetration of the ZP by further spermatozoa. The necessary element that initiates oocyte activation is apparently the release of intracellular calcium (Ca(2+)) stored in the endoplasmic reticulum (ER). The exact mechanism via which Ca(2+) is released within the oocyte has not been yet clarified, and has been a matter of an ongoing debate. Today, the sperm factor hypothesis has gained general acceptance, according to which a sperm molecule, either phospholipase C (PLCζ) or a post-acrosomal sheath WW domain-binding protein (PAWP), diffuses into the ooplasm initiating a molecular cascade involving mainly the phosphoinositide pathway. Mounting evidence now indicates that these calcium oscillations are caused by a testis-specific PLC termed PLCζ, released into the oocyte following gamete fusion. Also, recently, PAWP has been proposed as an alternative sperm factor candidate. These different sperm candidates have led to a significant debate. This raises important questions as regards to the relative importance of these two proteins as diagnostic tools in reproductive medicine with therapeutic potential, indicating the need for further research. In the present mini review, the phenomenon of oocyte activation during fertilization as well as the existing controversy will be highlighted and the possible mechanisms that are involved in this process will be discussed. Finally, an explanation of the existing debate will be attempted.

Attenuation of the oestrogen positive feedback mechanism with the age in postmenopausal women.

OBJECTIVE: It has been reported that the positive feedback mechanism of oestrogens and progesterone is preserved, although attenuated, in late postmenopausal years. Whether this is also true for the positive feedback effect of oestrogens alone has not been investigated. DESIGN: Prospective intervention study. PATIENTS: Thirty healthy postmenopausal women. MEASUREMENTS: The women were divided into three groups according to the years since menopause (group I: 2-8 years, group II: 9-17 years, group III: 18-25 years). They were studied during a period of 41 days. Two acute experiments (EP) of exogenous oestradiol, given via skin patches, were performed from days 1 to 7 (EP1) and from days 35 to 41 (EP2) to induce an LH surge. Between the two experiments (days 7-34), oestradiol was given at the dose of 100 µg every 3 days, while oral progesterone was added from day 21 to day 34 in order to simulate a luteal phase. Blood samples were taken every 6 h during EP1 and EP2 as well as on days 8, 13, 20, 21, 27 and 34. FSH, LH, oestradiol and progesterone were measured in all blood samples. RESULTS: An LH surge occurred as a result of the oestradiol positive feedback mechanism in group I and in group II, in both EP1 and EP2. Peak LH values during the surge were significantly lower in group II than in group I in both experiments. None of the patients in group III displayed an LH surge. CONCLUSIONS: These results demonstrate for the first time a gradual attenuation of the pituitary response to oestrogenic provocation over a certain period following the menopause, with complete abolition after 20 years. It is suggested that the reserves of pituitary gonadotrophs diminish with age.

Single-nucleotide polymorphism rs 175080 in the MLH3 gene and its relation to male infertility.

PURPOSE: MLH3, a MutL homolog protein in mammals playing a role in DNA mismatch repair, is associated with spermatogenesis and male infertility. The purpose of the present study was to investigate the association of the single-nucleotide polymorphism (SNP), rs 175080 in the MLH3 gene, with sperm parameters in a Greek population. METHODS: The study included 300 men of couples undergoing in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET) treatments (years 2011-2013). Genomic DNA was extracted from 300 peripheral blood samples, and conventional quantitative real-time PCR was performed for genotyping. Of them, 122 were from men used as "controls" and 178 from men used as "cases." Allocation to the two groups was based on sperm concentrations (≥15 and <15 million/ml, respectively). Serum FSH, LH, estradiol, testosterone, and prolactin concentrations as well as sperm parameters were compared between three genotypes (GG, GA, and AA). Furthermore, the frequencies of these three genotypes were compared between "cases" and "controls." RESULTS: Anthropometric parameters and hormonal values did not differ significantly between the three genotypes. Significantly lower sperm concentrations were found in men with the AA genotype as compared to men with the GG and GA genotypes (p < 0.001). The AA genotype had the lower progressive motility values as compared to the other two genotypes (p < 0.05). Also, there was a significantly different distribution of the frequencies of the three genotypes between "cases" and "controls" (p < 0.001). CONCLUSIONS: It is suggested that the studied SNP in the MLH3 gene may be linked to oligozoospermia in Caucasian men of a certain area.

Effect of Anti-Müllerian hormone (AMH) and bone morphogenetic protein 15 (BMP-15) on steroidogenesis in primary-cultured human luteinizing granulosa cells through Smad5 signalling.

PURPOSE: To determine if there is any effect of AMH and BMP-15 on estradiol and progesterone production from primary-cultured human luteinizing granulosa cells, to delineate what is the effect of FSH on their actions and which are the possible mechanisms involved. METHODS: Luteinizing granulosa cells (GCs), obtained from follicular fluid of 30 women undergoing in vitro fertilization, were cultured, after a short 24-h preincubation period, in serum-free medium for 24 or/and 48 h in the presence/absence of various concentrations of AMH, BMP-15 and FSH alone or in combinations. Estradiol and progesterone production, SMAD5 phosphorylation and StAR expression were studied in parallel. Steroids were measured in culture-supernatant using enzyme-immunoassays, while Smad5-signaling pathway activation and StAR protein expression were assessed immunocytochemically. RESULT(S): We found that the treatment of AMH in GCs for 24/48 h attenuated FSH-induced estradiol production (p < 0.001), had no effect on basal estradiol levels, decreased basal progesterone production (p < 0.001) and FSH-induced StAR expression (p < 0.001). On the other hand, BMP-15 decreased basal estradiol levels (p < 0.001) and attenuated FSH-induced estradiol production (p < 0.001). Furthermore, BMP-15 reduced progesterone basal secretion (p < 0.001), an effect that was partially reversed by FSH (p < 0.01), probably via increasing StAR expression (p < 0.001). FSH-induced StAR expression was also attenuated by BMP-15 (p < 0.001). FSH, AMH and BMP-15 activated Smad-signaling pathway, as confirmed by the increase of phospo-Smad5 protein levels (p < 0.001 compared to control). CONCLUSION(S): AMH and BMP-15 by interacting with FSH affect the production of estradiol and progesterone from cultured luteinizing-granulosa cells possibly via Smad5-protein phosphorylation.

Attenuating activity of the ovary on LH response to GnRH during the follicular phase of the cycle.

OBJECTIVE: Oestradiol sensitizes the pituitary to GnRH, while gonadotrophin surge attenuating factor (GnSAF) may oppose this action. Using the LH response to GnRH during treatment with FSH as an in vivo bioassay for GnSAF, we tested the hypothesis that the augmented LH response to GnRH in the late follicular phase is related to reduced production of GnSAF from the ovulatory follicle. DESIGN: Prospective intervention study. PATIENTS: Ten healthy, normally cycling women. MEASUREMENTS: The LH response to 10 µg GnRH i.v. (ΔLH) was investigated on days 2 and 3 and on days v (follicle size 16-17 mm) and v + 1 of cycle 1 (control) and cycle 2. On days 2 and v, a single s.c. injection of either normal saline (cycle 1) or 450 IU recombinant FSH (cycle 2) was given after the end of the GnRH experiment. RESULTS: FSH injection increased both serum oestradiol and inhibin B. In cycle 1, ΔLH remained unchanged from days 2 to 3 but increased significantly from days v to v + 1. In contrast, in cycle 2, ΔLH decreased significantly from days 2 to 3 (P < 0·05) and showed a nonsignificant increase from day v to day v + 1. The percentage difference in ΔLH between cycle 1 and cycle 2 was similar on days 3 (-66·9 ± 17·5%) and v + 1 (-65·2 ± 3·6%). CONCLUSIONS: These results suggest that during the follicular phase of the menstrual cycle, GnSAF is produced by small antral follicles, while the contribution of the ovulatory follicle is minimal.

Novel aspects of the endocrinology of the menstrual cycle.

Ovarian control of gonadotrophin secretion is normally achieved via the feedback mechanisms mediated by oestradiol and progesterone. Evidence has been provided that nonsteroidal substances, such as inhibin A and B, participate in the negative feedback control of FSH secretion. Another nonsteroidal ovarian substance is gonadotrophin surge-attenuating factor (GnSAF), the activity of which is particularly evident in women undergoing ovulation induction. Accumulating evidence has suggested that GnSAF plays a physiological role during the menstrual cycle. In particular, this factor antagonizes the sensitizing effect of oestradiol on the pituitary response to gonadotrophin-releasing hormone during the follicular phase of the cycle. A hypothesis has been developed that, in the late follicular phase, the activity of GnSAF is reduced and this facilitates the sensitizing effect of oestradiol on the pituitary, thus enforcing the massive discharge of gonadotrophins at the midcycle LH surge. The interaction of oestradiol, progesterone and GnSAF on the hypothalamic-pituitary system provides a novel approach to explain the mechanisms which control LH secretion during the normal menstrual cycle. The ovarian control of gonadotrophin secretion during the normal menstrual cycle is achieved via negative and positive feedback mechanisms. The steroids oestradiol and progesterone are the main regulators; however, nonsteroidal substances, such as inhibin A and inhibn B, also participate. Accumulating evidence has demonstrated that another nonsteroidal ovarian substance, gonadotrophin surge-attenuating factor (GnSAF), plays a key role in the control of LH secretion during the follicular phase and at midcycle, providing thus a novel aspect in the ovarian control of gonadotrophin secretion during the human menstrual cycle. The ovarian control of gonadotrophin secretion during the normal menstrual cycle is achieved via negative and positive feedback mechanisms. The steroids oestradiol and progesterone are the main regulators; however, nonsteroidal substances, such as inhibin A and inhibn B, also participate. Accumulating evidence has demonstrated that another nonsteroidal ovarian substance, gonadotrophin surge-attenuating factor (GnSAF), plays a key role in the control of LH secretion during the follicular phase and at midcycle, providing thus a novel aspect in the ovarian control of gonadotrophin secretion during the human menstrual cycle.

Molecular and cellular mechanisms of sperm-oocyte interactions opinions relative to in vitro fertilization (IVF).

One of the biggest prerequisites for pregnancy is the fertilization step, where a human haploid spermatozoon interacts and penetrates one haploid oocyte in order to produce the diploid zygote. Although fertilization is defined by the presence of two pronuclei and the extraction of the second polar body the process itself requires preparation of both gametes for fertilization to take place at a specific time. These preparations include a number of consecutive biochemical and molecular events with the help of specific molecules and with the consequential interaction between the two gametes. These events take place at three different levels and in a precise order, where the moving spermatozoon penetrates (a) the outer vestments of the oocyte, known as the cumulus cell layer; (b) the zona pellucida (ZP); where exocytosis of the acrosome contents take place and (c) direct interaction of the spermatozoon with the plasma membrane of the oocyte, which involves a firm adhesion of the head of the spermatozoon with the oocyte plasma membrane that culminates with the fusion of both sperm and oocyte membranes (Part I). After the above interactions, a cascade of molecular signal transductions is initiated which results in oocyte activation. Soon after the entry of the first spermatozoon into the oocyte and oocyte activation, the oocyte's coat (the ZP) and the oocyte's plasma membrane seem to change quickly in order to initiate a fast block to a second spermatozoon (Part II). Sometimes, two spermatozoa fuse with one oocyte, an incidence of 1%-2%, resulting in polyploid fetuses that account for up to 10%-20% of spontaneously aborted human conceptuses. The present review aims to focus on the first part of the human sperm and oocyte interactions, emphasizing the latest molecular and cellular mechanisms controlling this process.

Growth hormone response to submaximal doses of ghrelin remains unchanged during the follicular phase of the cycle.

BACKGROUND: Previous data have shown that ghrelin-induced growth hormone (GH) secretion is augmented in women by exogenous but not by endogenous estrogens. The purpose of this study was to examine the response of GH to low-dose scheme of ghrelin administration in relation to physiological changes in estradiol levels during the normal menstrual cycle. METHODS: Ten normally cycling women were studied in two menstrual cycles. Two consecutive dosages of ghrelin (0.15 µg/kg and 0.30 µg/kg) were injected intravenously at 0 and 90 min in the early and late follicular phases of one cycle. Saline was injected in the preceding cycle. Blood samples were taken at -15, 0, 30, 60, 90, 120, 150 and 180 min. The GH response was assessed. RESULTS: Serum estradiol concentrations were significantly higher in the late than in the early follicular phase. After ghrelin, but not after saline administration, plasma ghrelin and serum GH levels increased significantly in both phases, peaking at 30 min and 120 min. The peak value at 120 min was significantly higher than at 30 min (P<0.001). There were no significant differences in ghrelin and GH levels between the two phases at all time points. CONCLUSIONS: The present results show no difference in GH response to two consecutive submaximal doses of ghrelin between the early and the late follicular phase of the cycle. It is suggested that estradiol is not possibly involved in the physiological process that regulates ghrelin-induced GH secretion in women during the normal menstrual cycle.

The progesterone positive feedback effect in women after ovariectomy.

Various ovarian substances regulate the secretion of gonadotrophins during the menstrual cycle, but there are still several unclarified issues. The aim of this study was to investigate the positive feedback effect of progesterone during the immediate period following ovariectomy. Experiments were performed in 12 normally cycling women (aged 39-49 years). Following abdominal hysterectomy plus bilateral ovariectomy performed on cycle day 3 (day 0), the women received either estradiol via skin patches (days 0-7, n = 6, group 1) or estradiol as above plus vaginal progesterone (days 1-7, n = 6, group 2). Serum estradiol values increased similarly in the two groups. After the operation, serum progesterone levels decreased significantly in group 1, while in group 2 they remained stable becoming higher than in group 1 (p < 0.05). An LH and an FSH surge occurred in group 2 with the values after the peak returning to the pre-surge baseline. In contrast, in group 1 LH and FSH levels following an initial decrease, increased gradually until the end of the experiment. These results demonstrate that, despite a variable response to estrogens, the positive feedback effect of progesterone remained intact immediately after ovariectomy in women. It is suggested that it is the combining action of estradiol and progesterone that can ensure the expression of a positive feedback mechanism in women.

A comprehensive review and update on human fertility cryopreservation methods and tools.

The broad conceptualization of fertility preservation and restoration has become already a major concern in the modern western world since a large number of individuals often face it in the everyday life. Driven by different health conditions and/or social reasons, a variety of patients currently rely on routinely and non-routinely applied assisted reproductive technologies, and mostly on the possibility to cryopreserve gametes and/or gonadal tissues for expanding their reproductive lifespan. This review embraces the data present in human-focused literature regarding the up-to-date methodologies and tools contemporarily applied in IVF laboratories' clinical setting of the oocyte, sperm, and embryo cryopreservation and explores the latest news and issues related to the optimization of methods used in ovarian and testicular tissue cryopreservation.