Identification of the source of inhibins at the time of conception provides a diagnostic role for them in very early pregnancy

GnRH agonist for triggering of final oocyte maturation: time for a change of practice?

BACKGROUND

GnRH agonist (GnRHa) triggering has been shown to significantly reduce the occurrence of ovarian hyperstimulation syndrome (OHSS) compared with hCG triggering; however, initially a poor reproductive outcome was reported after GnRHa triggering, due to an apparently uncorrectable luteal phase deficiency. Therefore, the challenge has been to rescue the luteal phase. Studies now report a luteal phase rescue, with a reproductive outcome comparable to that seen after hCG triggering.

METHODS

This narrative review is based on expert presentations and subsequent group discussions supplemented with publications from literature searches and the authors' knowledge. Moreover, randomized controlled trials (RCTs) were identified and analysed either in fresh IVF cycles with embryo transfer (ET), oocyte donation cycles or cycles without ET; risk differences were calculated regarding pregnancy rate and OHSS rate.

RESULTS

In fresh IVF cycles with ET (9 RCTs) no OHSS was reported after GnRHa triggering [0% incidence in the GnRHa group: risk difference 5% (with 95% CI: -0.07 to 0.02)]. Importantly, the delivery rate improved significantly after modified luteal support [6% risk difference in favour of the HCG group (95% CI: -0.14 to 0.2)] when compared with initial studies with conventional luteal support [18% risk difference (95% CI: -0.36 to 0.01)]. In oocyte donation cycles (4 RCTs) the OHSS incidence is 0% [10% risk difference (95% CI: 0.02-0.40)].

CONCLUSIONS

GnRHa triggering is a valid alternative to hCG triggering, resulting in an elimination of OHSS. After modified luteal support there is now a non-significant difference of 6% in delivery rate in favour of hCG triggering.

Midtrimester maternal serum inhibin A levels after multifetal pregnancy reduction

OBJECTIVE

To investigate the relationship between the maternal serum inhibin A concentrations and the number of fetuses. Further, the maternal serum inhibin A levels for twin pregnancies and multiple pregnancies reduced to twins in the second trimester were compared.

METHODS

Three groups of women with pregnancies following in vitro fertilization and embryo transfer were recruited for this study. Groups 1, 2 and 3 included 20 singleton pregnancies, 37 twin pregnancies, and 35 multifetal pregnancies, respectively. In group 3, multifetal reduction was performed during 10-12 weeks of gestation. Blood samples were obtained longitudinally at 10th, 12th, 15th and 18th week of gestation.

RESULTS

There was a significant association between the number of fetuses and maternal plasma inhibin A prior to multifetal reduction. The inhibin A levels were not significantly different between twin and multifetal reduced twin pregnancies at 15th and 18th weeks of gestation.

CONCLUSION

In multifetal reduction to twin pregnancies, the maternal serum levels of inhibin A decrease to the level of twin pregnancies during the second trimester. Therefore, inhibin A may be effectively used as a marker for Down syndrome screening in cases of twin pregnancy following multifetal reduction.

Serum inhibin A, VEGF and TNFα levels after triggering oocyte maturation with GnRH agonist compared with HCG in women with polycystic ovaries undergoing IVF treatment: a prospective randomized trial

BACKGROUND

We aimed to examine the serum levels of inhibin A, vascular endothelial growth factor (VEGF), tumour necrosis factor alpha (TNFalpha), estradiol (E2) and progesterone levels after triggering of final oocyte maturation with GnRH agonist compared with HCG in patients with polycystic ovaries (PCO) and to investigate the relationship between these markers and ovarian hyperstimulation syndrome (OHSS).

METHODS

Twenty-eight patients with PCO, undergoing controlled ovarian hyperstimulation with FSH and GnRH antagonist for IVF-embryo transfer treatment, were randomized for triggering of final oocyte maturation with GnRH agonist (GnRH agonist group, n = 15) or HCG (HCG group, n = 13). Blood samples were obtained on the day of randomization and thereafter every 2-7 days. Serum levels of inhibin A, VEGF, TNFalpha, E2 and progesterone, the incidence of OHSS, ovarian size and pelvic fluid accumulation were evaluated.

RESULTS

Serum inhibin A, E2 and progesterone levels were significantly lower in the GnRH agonist group compared with the HCG group, particularly on the day of embryo transfer (P < 0.0001). Serum VEGF and TNFalpha levels were similar between the two groups. Four patients in the HCG group developed severe OHSS, whereas no patient had any symptoms or signs of OHSS in the GnRH-agonist group (P < 0.05).

CONCLUSIONS

In patients with PCO treated with FSH/GnRH antagonist, final oocyte maturation with GnRH agonist instead of HCG reduces significantly inhibin A, E2 and progesterone levels during the luteal phase. This phenomenon reflects the inhibition of the corpus luteum function and may explain, at least in part, the mechanism of OHSS prevention in high-risk patients. Our results do not support a crucial role for VEGF or TNFalpha in OHSS.

Inhibins in female and male reproductive physiology: role in gametogenesis, conception, implantation and early pregnancy

A great deal of new information has arisen in the recent years concerning inhibin physiology and clinical relevance in reproductive medicine. It is now recognized that the two inhibin isoforms, named inhibin A and inhibin B, are produced by the gonads in the course of gamete maturation and in women have a different pattern of secretion throughout the menstrual cycle. Since inhibins are also produced by placenta and fetal membranes, it has been suggested that there is an involvement in physiological adaptation of pregnancy. Evidence from several sources has underlined the clinical usefulness of the measurement of inhibin-related proteins in the diagnosis and follow-up of different fertility disturbances and early pregnancy viability. In the male, inhibin B is produced in the testis, principally by the Sertoli cells. Inhibin B expression and secretion are positively correlated with Sertoli cell function, sperm number, and spermatogenic status and are negatively correlated with FSH. This review covers the most recent advances on the role of inhibins in human reproductive function. Considerable progress in the understanding of inhibin physiology has resulted from selective measurement of the two inhibin molecular forms, named inhibin A and B. Newly recognized alterations of inhibin levels in gynaecological diseases as well as in normal and pathological pregnancy are discussed, with particular emphasis on the potential clinical usefulness of assessing inhibin levels in serum and other biological fluids.

Inhibins and activins in pregnancy

Human placenta, decidua, and fetal membranes are the major sites of production and secretion of inhibin A and activin A in maternal serum, amniotic fluid, and umbilical cord blood. These tissues also express follistatin-related gene and betaglycan, the binding proteins of activin A and inhibin A, respectively, recently identified. They show a different expression throughout pregnancy, suggesting new functional roles into gestational tissues. The availability of suitable assays for measuring inhibin A and activin A lead us the possibility to investigate their secretion in healthy pregnancy. In addition, several evidences underline the potential role and the clinical usefulness of their measurement in the diagnosis, prevention, prognosis and follow-up of different gestational pathologies such as: threatened abortion, placental tumors, hypertensive disorders of pregnancy, intrauterine growth restriction, fetal hypoxia. The measurement of inhibin A and activin A into the biological fluids of pregnancy will offer in the future further possibilities in early diagnosis, prediction, and monitoring pregnancy diseases.

Activin and follistatin in female reproduction

Activin and follistatin were initially identified in the follicular fluid based on their effects on pituitary FSH secretion in the mid-1980s. It is now evident that activin, follistatin and activin receptors are widely expressed in many tissues where they function as autocrine/paracrine regulators of a variety of physiological processes including reproduction. The major function of follistatin is to bind to activin with high affinity and block activin binding to its receptors. Total activin A and follistatin are also found in the maternal circulation throughout pregnancy. Activin A levels are increased in abnormal pregnancies such as pre-eclampsia, fetal growth restriction and gestational hypertension. The placenta, vascular endothelial cells and activated peripheral mononuclear cells (PBMC) may all contribute to the raised levels of activin A in pre-eclampsia with unaltered follistatin in pre-eclamptic placenta, PBMCs or vascular endothelial cells suggesting the availability of 'free' activin A that could be biologically active in these cells.

[Inhibins, activins and anti-Müllerian hormone: structure, signalling pathways, roles and predictive value in reproductive medicine]

Anti-Müllerian hormone (AMH), inhibins and activins are members of the transforming growth factor (TGFbeta) superfamily and are known to have a variety of actions concerning reproduction, hormonogenesis, development processes and differentiation. Inhibins and activins are dimeric glycoproteins that are defined by their actions on the pituitary gonadotroph cells. AMH, inhibins and activins have a vast array of actions usually exerted through paracrine and endocrine mechanisms. The recent availability of specific inhibin assays has demonstrated that inhibin B is the relevant circulating inhibin form in the human male. Inhibin B seems to be a useful marker of spermatogenesis, but serum and seminal inhibin B levels are not predictive parameters for the selection of azoospermic men as candidates for testicular sperm extraction (TESE). AMH in seminal plasma may be important for sperm production, and is a good marker for sertoli cell development. It might be the only one seminal marker of spermatogenesis in non-obstructive azoospermia. Nevertheless, many of these studies were carried out with small patient numbers, and consequently must be interpreted with caution. In women ongoing assisted reproductive therapy (ART), day 3 inhibin B and AMH levels predict the number of oocytes retrieved, but cannot predict likelihood of pregnancy. Further studies are needed to determine if AMH and inhibin predict ART outcomes better than classical parameters (age, FSH levels and follicular ultrasonography). AMH and inhibin are also specific markers of Sertoli- and granulosa-cell origin in gonadal tumors.

Lower levels of inhibin A and pro-alphaC during the luteal phase after triggering oocyte maturation with a gonadotropin-releasing hormone agonist versus human chorionic gonadotropin

OBJECTIVE

To investigate the effect of triggering oocyte maturation with GnRH agonist on corpus luteum function by measuring luteal phase levels of inhibin A and pro-alphaC.

DESIGN

Prospective randomized trial.

SETTING

In vitro fertilization (IVF) program at a university hospital.

PATIENT(S)

Infertile women undergoing IVF-ET treatment.

INTERVENTION(S)

Controlled ovarian hyperstimulation with FSH and GnRH antagonist, triggering of final oocyte maturation with either hCG (n = 8) or GnRH agonist (n = 8), IVF-ET, and collection of blood samples every 2-3 days during the luteal phase.

MEASUREMENTS AND MAIN RESULTS

Luteal phase serum levels of inhibin A and pro-alphaC, P, and E(2).

RESULT(S)

Levels of inhibin A, pro-alphaC, estrogen, and P were significantly lower from day 4 to day 14 after triggering final oocyte maturation by GnRH agonist compared with hCG. Maximal luteal serum inhibin A and pro-alphaC levels were 91.5 +/- 23.6 and 184.1 +/- 23.5 pg/mL in the GnRH agonist-treated women compared with 464.7 +/- 209.1 and 7,351.6 +/- 934.3 pg/mL in women treated with hCG.

CONCLUSION(S)

Triggering final oocyte maturation with GnRH agonist instead of hCG in IVF cycles dramatically decreases luteal levels of inhibins, reflecting significant inhibition of the corpus luteum function. This effect may explain, at least in part, the mechanism of ovarian hyperstimulation syndrome prevention by the use of GnRH agonist.

Changes in inhibins and activin secretion in healthy and pathological pregnancies

Inhibin-related proteins are involved in the control of the feto-maternal communication required to maintain pregnancy. Human placenta, decidua, and fetal membranes are the major sites of production and secretion of activin A, inhibin A and inhibin B in maternal serum, amniotic fluid, and cord blood. The availability of suitable assays developed in the last years has enabled the measurement of inhibins and activin A in their dimeric forms, in order to investigate their role in physiological conditions of pregnancy. The studies conducted on inhibin-related proteins and human pregnancy suggested the possibility of an involvement of inhibin A and activin A in the pathogenesis of gestational diseases. In fact, several lines of evidence underline the potential role and the clinical usefulness of inhibin-related proteins measurement in the diagnosis, prevention, prognosis and follow-up of different gestational pathologies such as early pregnancy viability, Down's syndrome, fetal demise, pre-eclampsia, pregnancy-induced hypertension, preterm delivery and intrauterine growth restriction. The measurement of inhibin A and activin A into the biological fluids of pregnancy will offer in the future, further possibilities in the early diagnosis, prediction, and monitoring diseases of pregnancy.

Measurement of inhibin A and activin A in pregnancy--possible diagnostic applications

Knowledge of the roles of inhibins and activins has progressed rapidly since the development of a specific and sensitive assay that can be used for measurements on human serum and amniotic fluid samples. There is a sound theoretical basis for the role of transforming growth factor-beta family members in inflammatory processes, many of which are analogous to implantation, parturition and a variety of pathological conditions in pregnancy. This review explores the potential use of assays for inhibins and activins in clinical practice and suggests further areas for research.

Endocrinology of the peri-implantation period

Current research suggests that the appearance of endometrial integrins and pinopode appearance signal the opening of the receptive phase of the endometrium. These integrins may be activated by the interleukin-1 system (IL-1). IL-1beta, expressed by the blastocyst, induces vascular endothelial growth factor (VEGF) which, in turn, promotes angiogenesis and integrin expression in endometrial cells. The IL-1 system also triggers the expression of gamma interferon (IFN-gamma) from T lymphocytes. Decidual natural killer (NK) lymphocytes interact with invading trophoblast to generate leukaemia inhibitory factor (LIF). LIF induces uPA and gelatinase, enzymes which play a crucial role in trophoblastic invasion. Progesterone is a potent inhibitor of LIF, while oestrogen is a potent inducer. Oestrogen in serum reflects follicular IL-1beta level and correlates with the outcome of embryo transfer after in vitro fertilization (IVF). Progesterone induces nitric oxide (NO) synthesis in the decidua, and NO promotes local vasodilatation and uterine quiescenceMeasurement of placental protein 14 (PP14, glycodelin-A) in serum may be of value as a screening test for implantation potential. However, human chorionic gonadotrophin (hCG) remains the most reliable predictor of successful implantation and pregnancy viability. An ovulation + 14 hCG level < 50 IU/l is often predictive of a non-viable outcome, while an ovulation + 21 hCG of < 200 IU/l always indicates a non-viable pregnancy. hCG secretion by invading trophoblast appears to be negatively modulated by endothelin-1 (ET-1) and prostaglandin F(2alpha)(PGF2alpha), while tissue growth factors and collagenases are positive modulators of hCG expression.ProalphaC, an inhibin pro-monomer, may have some value in monitoring corpus luteum function. Inhibin A, activin A and follistatin all rises throughout pregnancy and peak at 36 weeks of gestation. Relaxin is another ovarian hormone that may have a role in predicting implantation. Relaxin induces placental protein 14 (PP14, glycodelin-A) expression in a receptive endometrium, and measurement of serum PP14 may be of value as a screening test for implantation potential.