Genetic conflicts in human pregnancy

Pregnancy has commonly been viewed as a cooperative interaction between a mother and her fetus. The effects of natural selection on genes expressed in fetuses, however, may be opposed by the effects of natural selection on genes expressed in mothers. In this sense, a genetic conflict can be said to exist between maternal and fetal genes. Fetal genes will be selected to increase the transfer of nutrients to their fetus, and maternal genes will be selected to limit transfers in excess of some maternal optimum. Thus a process of evolutionary escalation is predicted in which fetal actions are opposed by maternal countermeasures. The phenomenon of genomic imprinting means that a similar conflict exists within fetal cells between genes that are expressed when maternally derived, and genes that are expressed when paternally derived. During implantation, fetally derived cells (trophoblast) invade the maternal endometrium and remodel the endometrial spiral arteries into low-resistance vessels that are unable to constrict. This invasion has three consequences. First, the fetus gains direct access to its mother's arterial blood. Therefore, a mother cannot reduce the nutrient content of blood reaching the placenta without reducing the nutrient supply to her own tissues. Second, the volume of blood reaching the placenta becomes largely independent of control by the local maternal vasculature. Third, the placenta is able to release hormones and other substances directly into the maternal circulation. Placental hormones, including human chorionic gonadotropin (hCG) and human placental lactogen (hPL), are predicted to manipulate maternal physiology for fetal benefit. For example, hPL is proposed to act on maternal prolactin receptors to increase maternal resistance to insulin. If unopposed, the effect of hPL would be to maintain higher blood glucose levels for longer periods after meals. This action, however, is countered by increased maternal production of insulin. Gestational diabetes develops if the mother is unable to mount an adequate response to fetal manipulation. Similarly, fetal genes are predicted to enhance the flow of maternal blood through the placenta by increasing maternal blood pressure. Preeclampsia can be interpreted as an attempt by a poorly nourished fetus to increase its supply of nutrients by increasing the resistance of its mother's peripheral circulation.

Ovarian hyperstimulation syndrome in novel reproductive technologies: prevention and treatment

OBJECTIVE

To overview the world literature on ovarian hyperstimulation syndrome (OHSS) and modes of prevention and treatment of OHSS.

STUDY SELECTION

All the pertinent literature on OHSS, its prevention, and strategies for treatment were reviewed.

PREVENTION

Key to prevention is proper identification of the population at risk, which includes women with either the hormonal or the morphological signs of polycystic ovarian disease, high serum estradiol (E2) before human chorionic gonadotropin (hCG) administration (E2 greater than 4,000 pg/mL), multiple follicular response (greater than 35), younger age, and lean habitus. When a high risk situation is recognized, ovulatory dose of hCG may be reduced, avoided (with cycle cancellation), or substituted by gonadotropin-releasing hormone or its agonist. Luteal support with hCG is to be bypassed. To minimize risk of OHSS, endogenous pregnancy-drived hCG may be eluded by judicious cryopreservation of all embryos. Last, follicular aspiration will allow higher levels of E2 and larger number of follicles to be matured with lesser risk of OHSS than conventional ovulation induction without follicular aspiration.

TREATMENT

In-house for the severe and intensive care for the critical form. Meticulous fluid and electrolyte balance using both crystalloids and colloids (albumin) until hemoconcentration abates. Paracentesis is indicated for tight ascites, deteriorating kidney functions, and symptomatic relief. Diuretics may be prudently used once hemodilution is achieved. Dopamine drip may be used as a renal rescue, whereas heparin is indicated for thromboembolic phenomena and surgery reserved for abdominal catastrophies. Therapeutic interruption of an early gestation may be lifesaving when all other measures have failed.

CONCLUSIONS

Although severe and critical OHSS may not be completely avoided, early recognition of high-risk factors, judicious prevention schemes, and treatment strategies should reduce the complication and long-term sequelae of this iatrogenic syndrome.

Biological functions of hCG and hCG-related molecules

BACKGROUND

hCG is a term referring to 4 independent molecules, each produced by separate cells and each having completely separate functions. These are hCG produced by villous syncytiotrophoblast cells, hyperglycosylated hCG produced by cytotrophoblast cells, free beta-subunit made by multiple primary non-trophoblastic malignancies, and pituitary hCG made by the gonadotrope cells of the anterior pituitary.

RESULTS AND DISCUSSION

hCG has numerous functions. hCG promotes progesterone production by corpus luteal cells; promotes angiogenesis in uterine vasculature; promoted the fusion of cytotrophoblast cell and differentiation to make syncytiotrophoblast cells; causes the blockage of any immune or macrophage action by mother on foreign invading placental cells; causes uterine growth parallel to fetal growth; suppresses any myometrial contractions during the course of pregnancy; causes growth and differentiation of the umbilical cord; signals the endometrium about forthcoming implantation; acts on receptor in mother's brain causing hyperemesis gravidarum, and seemingly promotes growth of fetal organs during pregnancy. Hyperglycosylated hCG functions to promote growth of cytotrophoblast cells and invasion by these cells, as occurs in implantation of pregnancy, and growth and invasion by choriocarcinoma cells. hCG free beta-subunit is produced by numerous non-trophoblastic malignancies of different primaries. The detection of free beta-subunit in these malignancies is generally considered a sign of poor prognosis. The free beta-subunit blocks apoptosis in cancer cells and promotes the growth and malignancy of the cancer. Pituitary hCG is a sulfated variant of hCG produced at low levels during the menstrual cycle. Pituitary hCG seems to mimic luteinizing hormone actions during the menstrual cycle.

The presence of gonadotropin receptors in nonpregnant human uterus, human placenta, fetal membranes, and decidua

The possible presence of gonadotropin receptors in nonpregnant human uterus and human fetoplacental unit was investigated by light microscope immunocytochemistry using a monoclonal antibody to rat luteal hCG/LH receptors. The receptor antibody cross-reacted with human and bovine hCG/LH receptors and appears to be directed against the receptor rather than other proteins, including HLA class I antigens. Uterus and fetoplacental unit contained receptor antibody-binding sites, which indicates the presence of hCG/LH receptors. In the endometrium these receptors were present in glandular and luminal epithelial cells as well as in stromal cells. In the myometrium the receptors were detected in circular and elongated myometrial smooth muscle and vascular smooth muscle. Comparison of immunostaining intensities, which indicates the presence of different amounts of receptors, revealed that luminal and glandular epithelial cells contained more receptors than stromal cells. These cells, in turn, contained more receptors than myometrial and vascular smooth muscle. All cells in secretory phase uterine specimens contained more receptors than corresponding cells from the proliferative phase of the cycle. Midpregnancy placenta, amniotic epithelium, chorionic cytotrophoblasts, and decidual cells contained hCG/LH receptors. At term pregnancy, while receptors in fetal membranes and decidua continue to be detected, placental tissues did not show any detectable receptors unless the tissues were pretreated with neuraminidase. This indicated that term pregnancy placenta contain hCG/LH receptors masked by sialic acid residues. Comparison of immunostaining intensities suggested that syncytiotrophoblasts contained more receptors than cytotrophoblasts at midpregnancy; mesenchymal cells or blood vessels contained no detectable receptors. There were more receptors in decidua than in fetal membranes at mid- and term pregnancy. While the amniotic epithelial receptors decreased, the receptors in chorionic cytotrophoblasts and decidual cells increased from mid- to term pregnancy. In summary, hCG/LH receptors were demonstrated in the nonpregnant human uterus, human placenta, fetal membranes, and decidua. This indicates that hCG/LH may directly regulate functions of these tissues by endocrine, autocrine, or paracrine mechanisms.

Human trophoblast function during the implantation process

The implantation process involves complex and synchronized molecular and cellular events between the uterus and the implanting embryo. These events are regulated by paracrine and autocrine factors. Trophoblast invasion and migration through the uterine wall is mediated by molecular and cellular interactions, controlled by the trophoblast and the maternal microenvironment. This review is focused on the molecular constituents of the human trophoblast, their actions and interactions, including interrelations with the uterine endometrium.

Pituitary control of ovarian function--concepts derived from gonadotrophin therapy

From experience gained in the monitoring of ovarian responses to gonadotropin therapy, it has been possible to develop concepts concerning the mechanisms which operate during the normal menstrual cycle. It is shown that the ovarian requirement for FSH operates in a very narrow range, involving changes in concentration of only 10%; this range operates from a threshold level, through an intermediate level to a maximum level. After adequate stimulation, the follicle goes through a costing phase during which it is independent of further FSH stimulation and it acquires sensitivity to LH. Methods for determining optimum requirements for FSH and HCG for the induction of singleton pregnancies are presented. The relevance of the findings in providing hypotheses explaining some aspects of ovulatory and anovulatory cycles are discussed.

Estradiol-17beta stimulates the renewal of spermatogonial stem cells in males

In this work, we examined the functions of the female hormone "estrogen" on spermatogenesis of the Japanese eel (Anguilla japonica). Estradiol-17beta (E(2)), a natural estrogen in vertebrates, was present in the serum and its receptor was expressed in the testis during the whole process of spermatogenesis. Spermatogonial stem cell renewal was promoted by E(2) implantation but was suppressed by tamoxifen (an antagonist of estrogen). In vitro, 10 pg/ml of E(2) was sufficient to induce spermatogonial stem cell division in cultured testicular tissue, therefore confirming the in vivo observations. These results clearly show that estrogen is an indispensable "male hormone" in the early spermatogenetic cycle.

LH and hCG action on the same receptor results in quantitatively and qualitatively different intracellular signalling

Human luteinizing hormone (hLH) and chorionic gonadotropin (hCG) act on the same receptor (LHCGR) but it is not known whether they elicit the same cellular and molecular response. This study compares for the first time the activation of cell-signalling pathways and gene expression in response to hLH and hCG. Using recombinant hLH and recombinant hCG we evaluated the kinetics of cAMP production in COS-7 and hGL5 cells permanently expressing LHCGR (COS-7/LHCGR, hGL5/LHCGR), as well as cAMP, ERK1/2, AKT activation and progesterone production in primary human granulosa cells (hGLC). The expression of selected target genes was measured in the presence or absence of ERK- or AKT-pathways inhibitors. In COS-7/LHCGR cells, hCG is 5-fold more potent than hLH (cAMP ED₅₀: 107.1±14.3 pM and 530.0±51.2 pM, respectively). hLH maximal effect was significantly faster (10 minutes by hLH; 1 hour by hCG). In hGLC continuous exposure to equipotent doses of gonadotropins up to 36 hours revealed that intracellular cAMP production is oscillating and significantly higher by hCG versus hLH. Conversely, phospho-ERK1/2 and -AKT activation was more potent and sustained by hLH versus hCG. ERK1/2 and AKT inhibition removed the inhibitory effect on NRG1 (neuregulin) expression by hLH but not by hCG; ERK1/2 inhibition significantly increased hLH- but not hCG-stimulated CYP19A1 (aromatase) expression. We conclude that: i) hCG is more potent on cAMP production, while hLH is more potent on ERK and AKT activation; ii) hGLC respond to equipotent, constant hLH or hCG stimulation with a fluctuating cAMP production and progressive progesterone secretion; and iii) the expression of hLH and hCG target genes partly involves the activation of different pathways depending on the ligand. Therefore, the LHCGR is able to differentiate the activity of hLH and hCG.

New discoveries on the biology and detection of human chorionic gonadotropin

Human chorionic gonadotropin (hCG) is a glycoprotein hormone comprising 2 subunits, alpha and beta joined non covalently. While similar in structure to luteinizing hormone (LH), hCG exists in multiple hormonal and non-endocrine agents, rather than as a single molecule like LH and the other glycoprotein hormones. These are regular hCG, hyperglycosylated hCG and the free beta-subunit of hyperglycosylated hCG. For 88 years regular hCG has been known as a promoter of corpus luteal progesterone production, even though this function only explains 3 weeks of a full gestations production of regular hCG. Research in recent years has explained the full gestational production by demonstration of critical functions in trophoblast differentiation and in fetal nutrition through myometrial spiral artery angiogenesis. While regular hCG is made by fused villous syncytiotrophoblast cells, extravillous invasive cytotrophoblast cells make the variant hyperglycosylated hCG. This variant is an autocrine factor, acting on extravillous invasive cytotrophoblast cells to initiate and control invasion as occurs at implantation of pregnancy and the establishment of hemochorial placentation, and malignancy as occurs in invasive hydatidiform mole and choriocarcinoma. Hyperglycosylated hCG inhibits apoptosis in extravillous invasive cytotrophoblast cells promoting cell invasion, growth and malignancy. Other non-trophoblastic malignancies retro-differentiate and produce a hyperglycosylated free beta-subunit of hCG (hCG free beta). This has been shown to be an autocrine factor antagonizing apoptosis furthering cancer cell growth and malignancy. New applications have been demonstrated for total hCG measurements and detection of the 3 hCG variants in pregnancy detection, monitoring pregnancy outcome, determining risk for Down syndrome fetus, predicting preeclampsia, detecting pituitary hCG, detecting and managing gestational trophoblastic diseases, diagnosing quiescent gestational trophoblastic disease, diagnosing placental site trophoblastic tumor, managing testicular germ cell malignancies, and monitoring other human malignancies. There are very few molecules with such wide and varying functions as regular hCG and its variants, and very few tests with such a wide spectrum of clinical applications as total hCG.

Human chorionic gonadotropin: its possible role in maternal lymphocyte suppression

Human chorionic gonadotropin completely inhibits the response of lymphocytes to phytohemagglutinin. The effect is both reversible and noncytotoxic. These observations support the theory that the fetus is accepted because human chorionic gonadotropin represents trophoblastic surface antigen and blocks the action of maternal lymphocytes.

What happens to the normal thyroid during pregnancy?

Hormonal changes and metabolic demands during pregnancy result in profound alterations in the biochemical parameters of thyroid function. For the thyroidal economy, the main events occurring during pregnancy are: a marked increase in serum thyroxine-binding globulin levels; a marginal decrease in free hormone concentrations (in iodine-sufficient conditions) that is significantly amplified when there is iodine restriction or overt iodine deficiency; a frequent trend toward a slight increase in basal thyrotropin (TSH) values between the first trimester and term; a direct stimulation of the maternal thyroid gland by elevated levels of human chorionic gonadotropin (hCG), which occurs mainly near the end of the first trimester and can be associated with a transient lowering in serum TSH; and finally, modifications of the peripheral metabolism of maternal thyroid hormones. Together, metabolic changes associated with the progression of gestation in its first half constitute a transient phase from a preconception steady-state to the pregnancy steady-state. In order to be met, these metabolic changes require an increased hormonal output by the maternal thyroid gland. Once the new equilibrium is reached, increased hormonal demands are maintained until term, probably through transplacental passage of thyroid hormones and increased turnover of maternal thyroxine (T4), presumably under the influence of the placental (type III) deiodinase. For healthy pregnant women with iodine sufficiency, the challenge of the maternal thyroid gland is to adjust the hormonal output in order to achieve the new equilibrium state, and thereafter maintain the equilibrium until term. In contrast, the metabolic adjustment cannot easily be reached when the functional capacity of the thyroid gland is impaired (such as in autoimmune thyroid disease and hypothyroidism) or when pregnancy takes place in healthy women residing in areas with a deficient iodine intake. The ideal dietary allowance of iodine recommended by the World Health Organization (WHO) is 200 microg iodine per day for pregnant women. In conditions with iodine restriction, enhanced thyroidal stimulation is revealed by relative hypothyroxinemia and goitrogenesis. Goiters formed during gestation may only partially regress after parturition. Pregnancy, therefore, represents one of the environmental factors that may explain the higher prevalence of goiter and thyroid disorders in the female population. An iodine-deficient status in the mother also leads to goiter formation in the progeny. When adequate iodine supplementation is given early during pregnancy, it allows for the correction and almost complete prevention of maternal and neonatal goitrogenesis. In summary, pregnancy is accompanied by profound alterations in the thyroidal economy, resulting from a complex combination of factors specific to the pregnant state, which together concur to stimulate the maternal thyroid machinery. Increased thyroidal stimulation induces, in turn, a sequence of events leading from physiological adaptation of the thyroidal economy observed in healthy iodine-sufficient pregnant women, to pathological alterations, affecting both thyroid function and the anatomical integrity of the thyroid gland, when gestation takes place in conditions with iodine restriction or deficiency: the more severe the iodine deficiency, the more obvious, frequent, and profound the potential maternal and fetal repercussions.

The classification, functions and clinical use of different isoforms of HCG

HCG is composed of two subunits, HCGalpha and HCGbeta. During early pregnancy, HCG stimulates progesterone production in the corpus luteum, and injection of HCG is widely used to induce ovulation in assisted reproduction treatment (ART). Under experimental conditions, the free subunits have been shown to exert functions other than those of HCG, but the relevance of these remains to be determined. Intact HCG, free subunits and degraded forms of these occur in biological fluids, and determinations of these are important for diagnosis and monitoring of pregnancy, pregnancy-related disorders and several types of cancer. Development of optimal methods for the various forms has been hampered by lack of appropriate standards and expression of the concentrations of the various forms in units that are not comparable. Furthermore, the nomenclature for HCG assays is confusing and in some cases misleading. These problems can now be solved; a uniform nomenclature has been established, and new standards are available for HCG, its subunits HCGalpha and HCGbeta, the partially degraded or nicked forms of HCG and HCGbeta, and the beta-core fragment. This review describes the biochemical and biological background for the clinical use of determinations of various forms of HCG. The clinical use of HCG and studies on HCG vaccines are briefly reviewed.

On the role of human chorionic gonadotropin (hCG) in the embryo-endometrial microenvironment: implications for differentiation and implantation

Recent evidence suggests that human chorionic gonadotropin (hCG), in addition to its well-known endocrine effects on the corpus luteum, may act as a growth and differentiation factor during pregnancy. According to experimental results, its mode of action may be divided into three sequential phases. During the first phase, which begins at the blastocyst stage and lasts until the occurrence in the serum, hCG acts preferentially in a juxtacrine manner. We have used an intrauterine microdialysis system developed in our laboratory to administer low concentrations of hCG to the endometrium of women in the luteal phase of the menstrual cycle. HCG administration provoked profound effects on paracrine parameters of differentiation (IGFBP-1, prolactin) and implantation (LIF, M-CSF). VEGF, a cytokine important for neoangiogenesis, was significantly stimulated by hCG (P < .01), suggesting a role for hCG in the control of endometrial vascularization and placentation. The investigation of endometrial parameters of tissue remodeling revealed a significant increase of MMP-9 (P < .05) but not of TIMP-1 following hCG infusion. The second, endocrine, phase of hCG action is marked by the appearance of hCG in the maternal serum. Rising systemic hCG levels cause a very rapid elevation of serum progesterone reflecting the rescue of the corpus luteum. Other endocrine functions of hCG include its intrinsic thyrotropic activity as well as modulation of fetal testicular, ovarian, and adrenal function. The third phase may be characterized by the expression of full-length hCG/LH receptors on the trophoblasts themselves. Before the ninth week of gestation, human villous trophoblasts express a truncated hCG/LH receptor isoform (50 kDa) and are probably not responsive to hCG. Later, the expression pattern is switched to the full-length receptor (80 kDa), allowing hCG also to modulate the differentiation of the trophoblasts themselves. A special feature is the self-regulation of hCG biosynthesis that may in part explain the unique secretion profile of the hormone with peak levels during the first trimester followed by a rapid decline after the tenth week of gestation. In summary, hCG seems to have a variety of local and systemic functions in and outside the embryo-endometrial microenvironment.

The pathophysiology of ovarian hyperstimulation syndrome--views and ideas

Ovarian hyperstimulation syndrome (OHSS) is a serious complication affecting ovulation induction. Its most severe manifestation takes the form of massive ovarian enlargement and multiple cysts, haemoconcentration and third-space accumulation of fluid. The full-blown clinical syndrome may be complicated by renal failure and oliguria, hypovolaemic shock, thromboembolic episodes, adult respiratory distress syndrome (ARDS), and death. Although the pathophysiology of this syndrome has not been completely elucidated, it seems likely that the increased capillary permeability triggered by the release of vasoactive substance secreted by the ovaries under human chorionic gonadotrophin (HCG) stimulation plays a key role in this syndrome. Several factors such as histamine, serotonin, prostaglandins, prolactin, and a variety of other substances have been implicated in this process in the past. At present, factors belonging to the renin-angiotensin system, cytokines including the interleukins, tumour necrosis factor alpha, endothelin-1 and vascular endothelial growth factor (VEGF) are thought to be involved in triggering increased vascular permeability after ovulation induction treatment. This manuscript summarizes the current knowledge of the pathophysiology of ovarian hyperstimulation syndrome with emphasis on the correlation of the various factors with the clinical phenomena of this iatrogenic syndrome.

The biological role of the carboxyl-terminal extension of human chorionic gonadotropin [corrected] beta-subunit

hCG is a member of a family of glycoprotein hormones which share a common alpha-subunit, but differ in their hormone-specific beta-subunits. The CG beta-subunit is unique in that it contains a hydrophilic carboxyl-terminal extension with four serine O-linked oligosaccharides. To examine the role of the O-linked oligosaccharides and the carboxyl-terminal extension of hCG beta on receptor binding, steroidogenesis in vitro, and ovulation induction in vivo, site-directed mutagenesis and gene transfer methods were used. Wild-type hCG alpha and hCG beta expression vectors were transfected into an O-glycosylation mutant Chinese hamster ovary cell line to produce intact dimer hCG lacking the beta-subunit O-linked oligosaccharide units. In addition, a mutant hCG beta gene (CG beta delta T) was generated which contained a premature termination signal at codon 115. This gene was cotransfected with the hCG alpha gene into Chinese hamster ovary cells to produce hCG dimer which lacked the carboxyl-terminal amino acids 115-145 of hCG beta (truncated hCG). The O-linked oligosaccharide deficient or truncated hCG derivatives were examined for their ability to bind to the mouse LH/hCG receptor and stimulate cAMP and steroidogenesis in vitro. These studies show that the O-linked oligosaccharides and carboxyl-terminal extension play a minor role in receptor binding and signal transduction. In contrast, comparison of the stimulatory effects of truncated and wild-type hCG in a rat ovulation assay in vivo via either intrabursal or iv injection revealed that the truncated derivative was approximately 3-fold less active than wild-type hCG. These findings indicate that the carboxyl-terminal extension of hCG beta and associated O-linked oligosaccharides are not important for receptor binding or in vitro signal transduction, but are critical for in vivo biological responses.

Regulation and action of angiogenic factors in the primate ovary

The ephemerality of the maturing follicle and subsequent corpus luteum as they perform their gametogenic and/or endocrine functions during the ovarian cycle is associated with remarkable changes in local vasculature. Studies on the angiogenic and angiolytic process in the ovary, rare in healthy adult tissues, complement recent efforts to understand vasculogenesis in embryonic tissues and to control angiogenesis in pathologic states such as cancer. Several reports indicate that the newly discovered vascular-specific angiogenic factors are expressed in the ovary, notably members of the vascular endothelial growth factor (VEGF) and angiopoietin (Ang) families plus their receptors (VEGF-Rs, neuropilins, Tie). Unlike in many other tissues, gonadotropic hormones (particularly luteinizing hormone, [LH]) are major stimulators of angiogenesis and VEGF/Ang expression in the ovary. However, local factors such as insulin-like growth factors or oxygen tension likely modulate the angiogenic processes. Recent studies employing systemic or local administration of anti-angiogenic drugs (TNP-470 or fumagillin) or specific VEGF antagonists (VEGF antibody or soluble VEGFR-1) demonstrate a vital role for normal angiogenesis and VEGF action in follicle development, ovulation, or corpus luteum function. Further studies discerning the various angiogenic factors and their roles in controlling the growth, maturation, function, and regression of the vasculature in ovarian compartments during the menstrual cycle could yield novel strategies for manipulating fertility or for alleviating infertility.

Physiological and pathological aspects of the effect of human chorionic gonadotropin on the thyroid

Human chorionic gonadotropin (hCG) is a glycoprotein hormone that has structural similarity to TSH. At the time of the peak hCG levels in normal pregnancy, serum TSH levels fall and bear a mirror image to the hCG peak. This reduction in TSH suggests that hCG causes an increased secretion of T4 and T3. Women with hyperemisis gravidarum often have high hCG levels that cause transient hyperthyroidsm. In the vast majority of such patients, there will be spontaneous remission of the increased thyroid function when the vomiting stops in several weeks. When there are clinical features of hyperthyroidism, it is be reasonable to treat with antithyroid drugs or a beta-adrenergic blocker, but treatment is rarely required beyond 22 weeks of gestation. Hyperthyroidism or increased thyroid function has been reported in many patients with trophoblastic tumors, either hydatiditform mole or choriocarcinoma. The diagnosis of hydatidiform mole is made by ultrasonography that shows a 'snowstorm' appearance without a fetus. Hydatidiform moles secrete large amounts of hCG proportional to the mass of the tumor. The development of hyperthyroidism requires hCG levels of >200 U/ml that are sustained for several weeks. Removal of the mole cures the hyperthyroidism. There have been many case reports of hyperthyroidism in women with choriocarcinoma and high hCG levels. The principal therapy is chemotherapy, usually given at a specialized center. With effective chemotherapy, long-term survival exceeds 95%. A unique family with recurrent gestational hyperthyroidism associated with hyperemesis gravidarum was found to have a mutation in the extracellular domain of the TSH receptor that made it responsive to normal levels of hCG.

Novel concepts of human chorionic gonadotropin: reproductive system interactions and potential in the management of infertility

OBJECTIVE

To extensively review the scientific literature on the potential sites of hCG action and the role of this hormone on reproductive processes not necessarily related to the classic hCG functions of supporting early pregnancy.

DESIGN

Review of the international scientific literature and the authors' personal research experience in this area.

RESULT(S)

The LH/hCG receptor has an almost ubiquitous distribution in reproductive organs, thus suggesting that the actions of hCG might be more extensive than previously thought. Independently of FSH, low-dose hCG can support development and maturation of larger ovarian follicles that have acquired granulosa cells LH/hCG receptors, potentially providing effective and safer ovulation induction regimens. Human chorionic gonadotropin seems to be capable of improving uterine receptivity by enhancing endometrial quality and stromal fibroblast function. Furthermore, through its actions on insulin-like growth factor binding protein-1 and vascular endothelial growth factor, hCG might stimulate endometrial angiogenesis and growth and extend the implantation window, thus making pregnancy more likely.

CONCLUSION(S)

Mounting evidence indicates that hCG could be mediating relevant actions enhancing fertility and the efficacy of therapeutic procedures used in the management of infertility. Greater understanding of the physiologic roles that hCG plays in human reproduction might suggest novel clinical applications for this traditional hormone of pregnancy.

Is human chorionic gonadotropin directly involved in the regulation of human implantation?

The regulation of human implantation is not fully understood. hCG as one of the earliest embryonal signals may be a major regulator in the parakrine embryo-endometrial communication. The expression of full-length hCG/LH-receptor mRNA could be demonstrated in human endometrium throughout the follicular and secretory phase of the menstrual cycle. In contrast, in early pregnancy decidua only truncated variants could be detected. To investigate direct effects of hCG on the human endometrium, an intrauterine microdialysis device was developed to measure parakrine mediators within the uterine cavity in vivo. Using this system, hCG was applied in the secretory phase and the endometrial response was evaluated. The administration of hCG (500 IU/ml) provoked a significant inhibition of intrauterine IGFBP-1 and M-CSF, while LIF, VEGF and MMP-9 were significantly stimulated. Taken together there appear to be multiple direct effects of hCG on the endometrium that precede the classical endocrine role of the hormone.

Human chorionic gonadotropin contributes to maternal immunotolerance and endometrial apoptosis by regulating Fas-Fas ligand system

The first known hormonal signal of the conceptus during implantation is human chorionic gonadotropin (hCG). Interestingly, increased apoptosis in human endometrium coincides with the implantation window. Factors from the fetal or placental origin as well as maternal hormonal factors are likely to have a potential role in the regulation of apoptotic signaling molecules. We hypothesized that hCG may be a placental link for the development of local maternal immunotolerance. Fas-Fas ligand (FasL) system is one of the apoptotic signaling pathways, shown to be important in the development of local immune tolerance during and after implantation. We report that hCG treatment decreases cell proliferation and increases apoptosis in endometrial cells. Moreover, hCG stimulates FasL mRNA and protein expression without affecting Fas mRNA in these cells. Interestingly, in coculture experiments, hCG-treated endometrial cells induce an increase in T cell apoptosis. Our in vivo results reveal that cells of early pregnancy decidua express strong FasL immunoreactivity, and decidual areas containing interstitial cytotrophoblasts have numerous TUNEL-positive cells. Compared with decidual areas devoid of interstitial cytotrophoblasts, we observed in decidual areas containing interstitial cytotrophoblasts clearly less amount of TUNEL-positive cells. These results suggest that hCG may be a link in the development of peritrophoblastic immune tolerance and may facilitate the trophoblast invasion by regulating proapoptotic molecules such as FasL in endometrial cells.

Review: hCGs: different sources of production, different glycoforms and functions

Human chorionic gonadotropin (hCG) is the first hormonal message from the placenta to the mother. It is detectable in maternal blood two days after implantation and behaves like an agonist of LH stimulating progesterone secretion by the corpus luteum. hCG has also a role in quiescence of the myometrium and local immune tolerance. Specific to humans, hCG is a complex glycoprotein composed of two glycosylated subunits. The α-subunit is identical to the pituitary gonadotropin hormones (LH, FSH, TSH), contains two N-glycosylation sites, and is encoded by a single gene (CGA). By contrast the β-subunits are distinct in each of the hormones and confer receptor and biological specificity. The hCG β-subunit contains two sites of N-glycosylation and four sites of O-glycosylation and is encoded by a cluster of genes (CGB). In this review, we will stress the importance of hCG glycosylation state, which varies with the stage of pregnancy, its source of production and in the pathology. It is well established that hCG is mainly secreted by the syncytiotrophoblast into maternal blood where it peaks around 8-10 weeks of gestation (WG). The invasive extravillous trophoblast also secretes hCG, and in particular like choriocarcinoma cells, hyperglycosylated forms of hCG (hCG-H). In maternal blood hCG-H is high during early first trimester. In addition to its endocrine role, hCG has autocrine and paracrine roles. It promotes formation of the syncytiotrophoblast and angiogenesis through LHCG receptor. In contrast, hCG-H stimulates trophoblast invasion and angiogenesis by interacting with the TGFβ receptor 2. hCG is largely used in antenatal screening and hCG-H represents a serum marker of early trophoblast invasion. Other abnormally glycosylated hCG are described in aneuploidies. In conclusion, hCG is the major pregnancy glycoprotein hormone, whose maternal concentration and glycan structure change all along pregnancy. Depending on its source of production, glycoforms of hCG display different biological activities and functions that are essential for pregnancy outcome.

hCG, the wonder of today's science

BACKGROUND

hCG is a wonder. Firstly, because hCG is such an extreme molecule. hCG is the most acidic glycoprotein containing the highest proportion of sugars. Secondly, hCG exists in 5 common forms. Finally, it has so many functions ranging from control of human pregnancy to human cancer. This review examines these molecules in detail.

CONTENT

These 5 molecules, hCG, sulfated hCG, hyperglycosylated hCG, hCG free beta and hyperglycosylated free beta are produced by placental syncytiotrophoblast cells and pituitary gonadotrope cells (group 1), and by placental cytotrophoblast cells and human malignancies (group 2). Group 1 molecules are both hormones that act on the hCG/LH receptor. These molecules are central to human menstrual cycle and human pregnancy. Group 2 molecules are autocrines, that act by antagonizing a TGF beta receptor. These molecules are critical to all advanced malignancies.

CONCLUSIONS

The hCG groups are molecules critical to both the molecules of pregnancy or human life, and to the advancement of cancer, or human death.

Serum levels of intact human chorionic gonadotropin (HCG) and its free alpha and beta subunits, in relation to maternal thyroid stimulation during normal pregnancy

The main objective of the present study was to present additional evidence of the potentially important thyrotropic role of hCG to regulate the maternal thyroid gland during normal pregnancy. Sequential determinations (first and last trimesters) of intact hCG, free alpha and beta-hCG subunits concentrations (using monoclonal IRMAs), and assessment of parameters of thyroid function and thyroid volume were carried out in 62 pregnant women who exhibited during the first trimester of gestation low TSH levels (< or = 0.20 mU/L), and compared to 276 pregnant women with normal TSH levels. The prevalence of having low serum TSH represented 18% of all pregnancies, with almost one half of cases who transiently had undetectable TSH levels. Lowering of TSH was associated with high hCG levels, and occurred primarily during the first trimester. About 10% of women with low TSH presented transient gestational thyrotoxicosis, frequently associated with vomiting. In comparison to control subjects, women with a suppressed serum TSH had significantly and markedly higher intact hCG and free beta-hCG subunit concentrations. The results suggest that TSH reduction may result from a relative oversecretion of both intact hCG and free beta-hCG subunits, compatible with three hypotheses: a) transient overexpression of the beta-hCG gene, leading to enhanced production of hCG heterodimer; b) increased glycosylation of circulating hCG, with in turn a prolonged half life; c) larger syncytiotrophoblast mass with increased hCG production.(ABSTRACT TRUNCATED AT 250 WORDS)