Deep learning as a predictive tool for fetal heart pregnancy following time-lapse incubation and blastocyst transfer

STUDY QUESTION

Can a deep learning model predict the probability of pregnancy with fetal heart (FH) from time-lapse videos?

SUMMARY ANSWER

We created a deep learning model named IVY, which was an objective and fully automated system that predicts the probability of FH pregnancy directly from raw time-lapse videos without the need for any manual morphokinetic annotation or blastocyst morphology assessment.

WHAT IS KNOWN ALREADY

The contribution of time-lapse imaging in effective embryo selection is promising. Existing algorithms for the analysis of time-lapse imaging are based on morphology and morphokinetic parameters that require subjective human annotation and thus have intrinsic inter-reader and intra-reader variability. Deep learning offers promise for the automation and standardization of embryo selection.

STUDY DESIGN, SIZE, DURATION

A retrospective analysis of time-lapse videos and clinical outcomes of 10 638 embryos from eight different IVF clinics, across four different countries, between January 2014 and December 2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The deep learning model was trained using time-lapse videos with known FH pregnancy outcome to perform a binary classification task of predicting the probability of pregnancy with FH given time-lapse video sequence. The predictive power of the model was measured using the average area under the curve (AUC) of the receiver operating characteristic curve over 5-fold stratified cross-validation.

MAIN RESULTS AND THE ROLE OF CHANCE

The deep learning model was able to predict FH pregnancy from time-lapse videos with an AUC of 0.93 [95% CI 0.92-0.94] in 5-fold stratified cross-validation. A hold-out validation test across eight laboratories showed that the AUC was reproducible, ranging from 0.95 to 0.90 across different laboratories with different culture and laboratory processes.

LIMITATIONS, REASONS FOR CAUTION

This study is a retrospective analysis demonstrating that the deep learning model has a high level of predictability of the likelihood that an embryo will implant. The clinical impacts of these findings are still uncertain. Further studies, including prospective randomized controlled trials, are required to evaluate the clinical significance of this deep learning model. The time-lapse videos collected for training and validation are Day 5 embryos; hence, additional adjustment would need to be made for the model to be used in the context of Day 3 transfer.

WIDER IMPLICATIONS OF THE FINDINGS

The high predictive value for embryo implantation obtained by the deep learning model may improve the effectiveness of previous approaches used for time-lapse imaging in embryo selection. This may improve the prioritization of the most viable embryo for a single embryo transfer. The deep learning model may also prove to be useful in providing the optimal order for subsequent transfers of cryopreserved embryos.

STUDY FUNDING/COMPETING INTEREST(S)

D.T. is the co-owner of Harrison AI that has patented this methodology in association with Virtus Health. P.I. is a shareholder in Virtus Health. S.C., P.I. and D.G. are all either employees or contracted with Virtus Health. D.G. has received grant support from Vitrolife, the manufacturer of the Embryoscope time-lapse imaging used in this study. The equipment and time for this study have been jointly provided by Harrison AI and Virtus Health.

Human embryo: a biological definition

This paper defines a human embryo from a biological standpoint that takes into account emerging technologies in reproductive science. The paper does not consider legal, moral, religious or social views. As the definition of a human embryo must reflect the multifactorial processes of development, an approach has been adopted which combines recognition of observed events with potential for further development. This acknowledges that fertilization and development are not static processes, and as such embryo status can only be defined by observation of specific markers. The following biological definition of 'human embryo' is proposed. A human embryo is a discrete entity that has arisen from either: the first mitotic division when fertilization of a human oocyte by a human sperm is complete or any other process that initiates organized development of a biological entity with a human nuclear genome or altered human nuclear genome that has the potential to develop up to, or beyond, the stage at which the primitive streak appears, and has not yet reached 8 weeks of development since the first mitotic division.

Enhanced sensitivity to steroid-negative feedback during breast-feeding: low-dose estradiol (transdermal estradiol supplementation) suppresses gonadotropins and ovarian activity assessed by inhibin B

Breast-feeding reduces fertility, and this seems to be related, in part, to an enhancement of the sensitivity of the GnRH system to the negative feedback effects of estradiol related to suckling. Previously, we showed that short-term treatment with small doses of estradiol delivered transdermally suppress plasma gonadotropin concentrations in breast-feeding women. We have now monitored the effects on ovarian function of longer-term low-dose estradiol treatment using plasma inhibin B and inhibin A concentrations and ultrasonography. Breast-feeding women (n = 45) using barrier methods of contraception were enrolled at 6 weeks postpartum and followed up to 18 weeks PP. Nineteen women agreed to being randomized to wear either an estrogen [transdermal estradiol supplementation (TES); n = 10; Estraderm, 50 microg/24 h] or a placebo (PL; n = 9) patch for 12 weeks, whereas the remaining 26 women acted as untreated controls. TES did not significantly increase plasma estradiol concentrations. Plasma FSH levels decreased from 6.1+/-0.8 U/L to 3.3+/-0.6 U/L after 2 weeks of treatment (P < 0.01) and were lower in the TES group compared with the PL group at all times during the treatment (at least P < 0.05). Plasma LH concentrations in the TES group were lower than in the PL group after 4, 6, 8, and 10 weeks of estrogen treatment (at least P < 0.05). Throughout the study, no ovarian follicles detected by ultrasound were greater than 10 mm in diameter. Nevertheless, after 2 weeks of treatment, plasma inhibin B concentrations were significantly lower in the TES group than in the PL group (15.5+/-5.8 vs. 64.9+/-11.1 ng/L; P < 0.01) and remained significantly (P < 0.01) suppressed throughout the treatment, suggesting a suppression of the functional ovarian activity during TES. Inhibin A levels remained low in all groups (3-45 ng/L) but were suppressed further by TES treatment with no levels greater than 7 ng/L. We conclude that low-dose estradiol treatment given as TES suppresses ovarian activity as measured by inhibins B and A by reducing the secretion of LH and FSH during breast-feeding for several weeks. This supports the concept that suckling-induced suppression of the GnRH system is associated with an enhancement of the negative effects of estradiol on the hypothalamic GnRH system. Furthermore, because the contraceptive efficacy of breast-feeding is complicated by the unpredictable early return of ovarian activity in some women, TES could be the basis for the development of a novel contraceptive for breast-feeding women.

Changes in insulin-like growth factor-binding protein-3 messenger ribonucleic acid in endothelial cells of the human corpus luteum: a possible role in luteal development and rescue

In the human menstrual cycle, extensive angiogenesis accompanies luteinization; and the process is physiologically important for corpus luteum (CL) function. During luteolysis, the vasculature collapses, and the endothelial cells die. In a conceptual cycle, the CL persists both functionally and structurally beyond the luteoplacental shift. Although luteal rescue is not associated with increased angiogenesis, endothelial survival is extended. Despite the central role of the luteal vasculature in fertility, the mechanisms regulating its development and demise are poorly understood. There is increasing evidence that insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) may be important effectors of luteal function. Here, we have found that IGFBP-3 messenger RNA is expressed in the endothelium of the human CL and that the levels of message change during luteal development and rescue by human CG. The signal was strong during the early luteal phase, but it showed significant reduction during the mid- and late luteal phases. Interestingly, administration of human CG caused a marked increase in the levels of IGFBP-3 messenger RNA in luteal endothelial cells that was comparable to that observed during the early luteal phase. We conclude that endothelial cell IGFBP-3 expression is a physiological property of the CL of menstruation and pregnancy. These observations raise the intriguing possibility that the regulated expression of endothelial IGFBP-3 may play a role in controlling angiogenesis and cell responses in the human CL by autocrine/paracrine mechanisms.

Cell proliferation and vascular morphology in the marmoset corpus luteum

Luteal formation is associated with angiogenesis and low progesterone production. Maximal mid-luteal phase progesterone production is concurrent with extensive vascularization, and luteolysis occurs when steroidogenesis decreases. Angiogenic cell proliferation and vascular changes have not been examined in the marmoset. The aim of this study was to examine vascular morphology throughout the luteal phase by identifying: (i) von Willebrand factor VIII antigen (vW)-immunopositive endothelial cells; (ii) Ki67-positive proliferating cells; and (iii) bromodeoxyuridine-positive proliferating cells. Marmoset corpora lutea were examined throughout the cycle, and natural regression was compared with induced luteolysis after administration of a prostaglandin F(2alpha) analogue or gonadotrophin-releasing hormone (GnRH) antagonist. Steroidogenic and endothelial cells were positive for proliferation markers. Endothelial cell proliferation was highest during luteal formation, then decreased and remained low during the luteal phase and functional regression, however endothelial cell proliferation increased during structural regression. Endothelial cell proliferation was unchanged by induced regression. The area of vW immunostaining was highest during luteal formation, decreased thereafter and remained constant during the luteal phase and regression. Distribution of immunostaining indicated the presence of an extensive capillary network, but during structural regression the numbers of capillaries decreased and numbers of microvessels increased. These results suggest that vascular changes are concurrent with changes in the functional status of the marmoset corpus luteum.

Steroidogenic enzyme expression in human corpora lutea in the presence and absence of exogenous human chorionic gonadotrophin (HCG)

In a human conception cycle, the expected decline in progesterone production by the corpus luteum during the late luteal phase is prevented by human chorionic gonadotrophin (HCG) secreted by the implanting blastocyst. This study investigated the expression of components of the synthetic pathway for progesterone in human corpora lutea in the presence and absence of HCG in vivo. Corpora lutea were obtained from: (i) normally cycling women at the time of hysterectomy and classified on the basis of the urinary luteinizing hormone (LH) surge as early (n = 3), mid- (n = 3), or late luteal (n = 3); or (ii) women who had received daily doubling doses of HCG (n = 3) to 'rescue' the corpus luteum. Expression patterns of steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side-chain cleavage (P450scc) and 3beta-hydroxysteroid dehydrogenase (3beta-HSD) were investigated by Northern blotting, in-situ hybridization and immunohistochemistry. Luteal 'rescue' with HCG was associated with the continued expression of these components. In the late luteal phase, in the absence of HCG, expression remained but was more variable. The expression of 3beta-HSD mRNA was significantly reduced during the luteal phase (P<0.01). In conclusion, during luteal 'rescue', HCG acts to maintain the steroidogenic pathway. In the absence of HCG, the decline in progesterone production begins in the presence of the main components of the steroidogenic pathway. While unlikely to initiate this decline, the altered expression levels of these components, particularly that of 3beta-HSD, may contribute to the continued reduction in progesterone production.

Ubiquitin and apoptosis in the corpus luteum of the marmoset monkey (Callithrix jacchus)

The polypeptide ubiquitin covalently binds to cytoplasmic proteins and marks them for proteolytic degradation. Ubiquitin is upregulated during apoptosis in some systems. Apoptosis increases during luteolysis but it is not known whether ubiquitin is expressed in regressing corpora lutea. Marmoset ovaries were removed on day 10 of the luteal phase from animals that had received either no treatment, treatment with the PGF2 alpha analogue cloprostenol 24 h earlier, or treatment with the GnRH antagonist antarelix for either 24 or 48 h before ovary collection. Ubiquitin was localized on ovarian sections by immunocytochemistry, and oligonucleosome formation characteristic of apoptosis was examined in isolated corpora lutea by electrophoresis of extracted [32P]DNA. Oligonucleosome formation was low in midluteal corpora lutea on day 10 but increased after induced luteal regression with PGF2 alpha and GnRH antagonist. Nuclear ubiquitin immunoreactivity was found in 1.66 +/- 0.66 steroidogenic cells and cytoplasmic staining was found in 0.4 +/- 0.3 steroidogenic cells (per x 40 field of view) in midluteal phase corpora lutea on day 10. Luteolytic induction with PGF2 alpha significantly increased the number of cells exhibiting cytoplasmic immunoreactivity to 12.24 +/- 1.6 (P < 0.05). Ubiquitin immunoreactivity was not observed after GnRH-induced luteal regression. Apoptotic oligonucleosome formation was found after induced luteal regression with both PGF2 alpha and GnRH antagonist, but ubiquitin upregulation only occurred after PGF2 alpha-induced regression. These results indicate that ubiquitin expression is not specific for luteolysis and is not an indicator of luteal apoptosis, but that the polypeptide does play a role in luteal cellular responses to PGF2 alpha.

The human corpus luteum: reduction in macrophages during simulated maternal recognition of pregnancy

It has been shown that immune cells, particularly macrophages, accumulate in the corpus luteum during luteolysis. This study aimed to investigate the effect of maternal recognition of pregnancy on the localization and numbers of macrophages in the human corpus luteum. Corpora lutea (n = 12) were obtained from normally cycling women at the time of hysterectomy and were dated on the basis of serial urinary luteinizing hormone (LH) estimation. In addition, corpora lutea (n = 4) were collected from women who had received daily doubling doses of human chorionic gonadotrophin (HCG) to mimic the hormonal changes of early pregnancy. Macrophages were localized by immunohistochemistry using an anti-CD68 antibody. Steroidogenic cells, steroidogenic cells of thecal origin and endothelial cells were identified on serial sections by immunohistochemistry for 3beta-hydroxysteroid dehydrogenase, 17alpha-hydroxylase and von Willebrand factor, respectively. The luteal cells capable of responding directly to HCG were identified by isotopic in-situ hybridization for messenger RNA encoding LH/HCG receptors. Macrophages were localized primarily to the vascular connective tissue and theca-lutein areas of the corpus luteum, although some were found in the granulosa-lutein cell layer. Macrophage numbers increased throughout the luteal phase to a maximum in the late-luteal phase (P < 0.05). Luteal 'rescue' with HCG was associated with a marked reduction in the numbers of tissue macrophages when compared with those of the late-luteal phase (P < 0.001). One of the effects of HCG during maternal recognition of pregnancy is to prevent the normal influx of macrophages into the corpus luteum. As LH/HCG receptors localized to the steroidogenic cells, this implies a fundamental role for steroidogenic cell products in the control of macrophage influx into the human corpus luteum.

Induced luteolysis in the primate: rapid loss of luteinizing hormone receptors

The molecular mechanisms involved in luteolysis are still unclear in the primate. This study aimed to investigate the effect of induced luteolysis on the ovarian luteinizing hormone (LH) receptor and the steroidogenic enzyme, 3beta-hydroxysteroid dehydrogenase (3beta-HSD) in the marmoset monkey. Luteolysis was induced in the mid-luteal phase either directly by systemic prostaglandin F2alpha (PGF2alpha), or indirectly by LH withdrawal using systemic gonadotrophin releasing hormone antagonist (GnRHant) treatment. The LH receptor was studied by isotopic mRNA in-situ hybridization and in-situ ligand binding and 3beta-HSD expression was studied using isotopic mRNA in-situ hybridization and immunohistochemistry. Induced luteolysis was associated with a reduction in the expression of LH receptor (P < 0.0001) and 3beta-HSD mRNA, closely followed by a reduction in the LH receptor (P < 0.05) and 3beta-HSD protein concentrations within 24 h. There were no differences in the findings whether luteolysis was induced with PGF2alpha or GnRHant. This study shows that disparate mechanisms to induce luteolysis in the primate result in an identical rapid loss of the LH receptor and 3beta-HSD. In conclusion, induced luteolysis leads to rapid loss of the steroidogenic pathway in luteal cells.

Immunolocalization of P450C17 in the mare corpus luteum

Although the mare corpus luteum (CL) is capable of aromatization, the expression of other enzymes involved in estradiol synthesis is not yet clear. This study examined the localization of P450C17 in the mare CL at different stages of its functional development. In ovaries from follicular phase mares P450C17 was localized in the theca cells of ovarian follicles. Following ovulation, no immunostaining for P450C17 was detected in the mature CLs of nonpregnant mares. In pregnant mares, no immunostaining for P450C17 was identified in the corpus luteum prior to secretion of eCG by the feto placental unit at Day 35 of pregnancy. The P450C17 was found to be expressed in CLs retrieved from Day 40 of pregnancy onwards. The changing expression of P450C17 raises the possibility that this may be a regulatory step for estrogen synthesis in the mare ovary.

The effect of luteal "rescue" on the expression and localization of matrix metalloproteinases and their tissue inhibitors in the human corpus luteum

Luteolysis is associated with tissue remodeling probably involving the matrix metalloproteinases (MMPs) and their specific tissue inhibitors (TIMPs). This study investigated the expression and localization of the major MMPs and TIMPs in the human corpus luteum throughout the luteal phase and after luteal rescue with hCG. Corpora lutea (n = 9) were collected at hysterectomy and were dated by serial urinary LH estimation. In addition, corpora lutea (n = 3) were collected from women who had received daily doubling doses of hCG to mimic the hormonal changes of early pregnancy. MMP-1, MMP-2, MMP-9, TIMP-1, TIMP-2, and TIMP-3 were investigated by zymography, reverse zymography, Northern blotting, and in situ hybridization. There was no change in the expression of MMP-1, TIMP-1, and TIMP-2 throughout the luteal phase or after luteal rescue. Little TIMP-3 could be detected in the corpus luteum. MMP-9 activity peaked in the early and late luteal phase. The expression and activity of MMP-2 were maximal in the late luteal phase. Exposure to hCG during luteal rescue in vivo was associated with a reduction (P < 0.05) in the expression and activity of MMP-2. Messenger ribonucleic acids (mRNAs) for MMP-1, MMP-2, and TIMP-2 were localized to the connective tissue stroma and the thecal-lutein cells of the corpus luteum. In contrast, TIMP-1 mRNA was localized to the granulosa-lutein cells, and MMP-9 mRNA was expressed in scattered cells within the steroidogenic and nonsteroidogenic cell layers. In conclusion, during maternal recognition of pregnancy, hCG prevents the normal increase in MMP-2 in the late luteal phase. MMPs can function in an environment containing large amounts of TIMP-1, as they have a different cellular localization.

The somatostatin analogue, octreotide, modifies both steroidogenesis and IGFBP-1 secretion in human luteinizing granulosa cells

The effect of the somatostatin analogue octreotide on the secretion of progesterone and insulin-like growth factor binding protein-1 (IGFBP-1) from human granulosa-luteal cells was investigated. Octreotide (10(-11), 10(-10) and 10(-9) M) alone induced a significant decrease in progesterone secretion (maximum suppression 69 +/- 5% of control: P < 0.0001). In contrast, treatment with octreotide in combination with human chorionic gonadotrophin (HCG), at 1 IU/ ml potentiated the stimulatory effect of HCG on progesterone secretion (HCG alone 201 +/- 3% of control: HCG + octreotide 10(-9) M 318 +/- 16%: P < 0.001). Treatment with octreotide increased the secretion of IGFBP-1 (maximum stimulation 254 +/- 25% of control: P < 0.01). No effect of HCG was seen on secretion of IGFBP-1. These findings raise the possibility that somatostatin may have a modulatory role in regulating steroidogenesis by the human corpus luteum. Further studies are required to establish the physiological significance of any such function.

Production of the proto-oncogene BAX does not vary with changing in luteal function in women

The mechanisms of luteal maintenance and regression in women are uncertain, but morphological and oligonucleosome studies raise the possibility that apoptosis may be involved. BAX is a proto-oncogene of the BCL-2 family which can induce apoptosis. The aim of this study was to determine whether BAX is expressed in the human corpus luteum and whether the level of expression changes relative to the stage of the luteal phase or in simulated early pregnancy. Carefully timed samples of corpus luteum were studied by immunostaining, sodium dodecyl sulphate-polyacrylamide gel electrophoresis and immunoblotting. BAX protein was immunolocalized in luteal sections from all stages including luteal rescue but BAX production did not change during luteal maintenance or regression. Localization of BAX to the steroid-secreting cells of the corpus luteum implies a functional role and BAX may interact with other members of the BCL-2 family to affect luteal function.

Cell death during luteal regression in the marmoset monkey (Callithrix jacchus)

The mechanism controlling luteal regression in primates is unknown but may involve cell death by apoptosis. Marmoset ovaries containing corpora lutea were studied at different stages of the normal ovarian cycle. Two additional groups of animals underwent induced luteolysis with either the prostaglandin F2 alpha analogue, cloprostenol, or the GnRH antagonist, antarelix, at the mid-luteal phase. Apoptosis in ovarian sections was estimated both by counting the number of cells exhibiting morphological features of apoptosis and by in situ labelling the 3' ends of the DNA fragments with digoxigenin-11-dUTP. Apoptosis was found to be significantly increased in corpora lutea in the early follicular phase (equivalent to the later stage of luteal lifespan) compared with the mid-luteal phase corpora lutea, as judged by either computerized morphometry or 3' end labelling. Apoptosis was also increased by the administration of either cloprostenol or antarelix when using the 3' end labelling end point, but only after cloprostenol when using computerized morphometry. A further form of cell death, characterized by the formation of cytoplasmic vacuoles, was also observed in corpora lutea undergoing both induced and spontaneous regression. These results demonstrate that apoptosis within the primate corpus luteum is increased in both physiological and induced luteal regression. In addition, they show that an alternative form of cell death is involved in both spontaneous and induced luteal regression, although the relative importance of the two mechanisms remains to be determined.

Endothelial cell proliferation follows the mid-cycle luteinizing hormone surge, but not human chorionic gonadotrophin rescue, in the human corpus luteum

The corpus luteum is essential for the maintenance of early pregnancy in women. Angiogenesis may be one factor involved in luteal rescue. The aim of this study was to determine the changes in endothelial cell proliferation throughout the luteal phase and in human chorionic gonadotrophin (HCG)-simulated early pregnancy. Human corpora lutea obtained throughout the luteal phase and in simulated early pregnancy were immunostained with antibodies for endothelial and proliferating cells. Number and distribution of endothelial and proliferating cells were examined. Endothelial cells were least abundant in the early luteal phase, increasing in the mid-luteal phase (P < 0.03). Endothelial numbers did not differ significantly between the late and the rescued corpora lutea. Endothelial cell proliferation was greatest in the early luteal phase and continued at a lower level during later stages. Simulated early pregnancy resulted in no change in endothelial cell proliferation. These results showed that a high degree of endothelial cell proliferation is associated with formation of the human corpus luteum. Unchanging levels of proliferation following HCG treatment (for 5-8 days from day 12 to day 16 post-ovulation, at 125 IU to 16,000 IU, following a daily doubling of dose) suggest that alternative processes are involved during luteal rescue.

Changes in dimeric inhibin A and B during normal early puberty in boys and girls

OBJECTIVE

Although recently developed specific and sensitive assays of bioactive dimeric inhibin A and B have given new insights into the pituitary-gonadal axis in adult men and during the adult female menstrual cycle, there have been no reports on circulating inhibin A and B during normal human puberty. The aim of this study was to assess the relationship of dimeric inhibin A and B to pubertal stage, FSH and testosterone or oestradiol in late prepuberty and in early puberty.

STUDY DESIGN AND SUBJECTS

Serial samples were collected during a prospective longitudinal trial of GH treatment in short normal children. Seven boys were studied from late prepuberty to genital stage 3, and six pre-menarche girls from late prepuberty to breast stage 4.

MEASUREMENTS

Dimeric inhibin A (girls only) and inhibin B (boys and girls) were measured by highly specific and sensitive two-site ELISAs, FSH by IRMA, testosterone and oestradiol by RIA.

RESULTS

In boys, inhibin B increased progressively from pubertal stages 1 to 3 (ANOVA P < 0.0001) and correlated strongly with mean testicular volume (r = 0.72, P = 0.0005). Prepubertal boys showed a positive correlation between inhibin B and FSH (r = 0.65, P = 0.056), whereas pubertal boys gave a strong negative correlation (r = 0.75, P = 0.012). In both prepubertal and pubertal boys positive correlations were observed between inhibin B (y) and testosterone (x) (r = 0.81, P = 0.008 and r = 0.62, P = 0.054 respectively), but the slope of the regression line between the two was much steeper before than after the onset of clinical puberty. In girls, both inhibin A and B increased through pubertal stages 1-4 (ANOVA P = 0.01 and P = 0.047 respectively). Both showed strong positive correlations with oestradiol (r = 0.80 and 0.79, P = 0.001) and with FSH (r = 0.83, P = 0.0004 and r = 0.80, P = 0.001). Inhibin A and B were also strongly correlated with each other (r = 0.92, P = 0.0001).

CONCLUSIONS

In boys, testicular production of inhibin B increases as puberty progresses. Our results show for the first time that the initiation of puberty is accompanied by a dramatic switch from a positive to a negative relation between inhibin B and FSH as inhibin B begins to exert the expected negative feedback on FSH. The results in girls suggest that, prior to menarche, the ovarian follicles produce inhibin A and B in strict proportion, and in progressively greater amounts as puberty proceeds. Measurement of dimeric inhibin A and B may provide a sensitive new tool for determining gonadal maturity in late prepuberty and early puberty.

Expression of tissue inhibitor of metalloproteinases-1 in the primate ovary during induced luteal regression

Although tissue inhibitor of metalloproteinases-1 (TIMP-1) is one of the major secretory products of the corpus luteum, the functional significance of this is not clear. In addition to its role as a specific inhibitor of the matrix metalloproteinase enzymes involved in tissue remodelling, it has recently been suggested that TIMP-1 is also a potent stimulator of steroidogenesis in vitro. However, in the ruminant, TIMP-1 expression increases during luteal regression. This study sought to determine (i) the effect of induced luteal regression on ovarian TIMP-1 expression in the primate and (ii) the expression of TIMP-1 in other steroidogenic and non-steroidogenic tissues. Marmoset ovaries were studied on day 10 of the normal luteal phase and 12 and 24 h after induced luteolysis, with either gonadotrophin-releasing hormone (GnRH) antagonist or prostaglandin F2 alpha analogue. Ovaries from different stages of the normal ovarian cycle were also studied. Expression of TIMP-1 was investigated by isotopic in situ hybridisation. TIMP-1 expression was also examined in a wide range of other marmoset tissues by Northern blotting and in situ hybridisation. TIMP-1 was found to be highly expressed in the marmoset corpus luteum. Luteolysis induced with either prostaglandin F2 alpha or GnRH antagonist was associated with a significant fall in TIMP-1 expression in luteal tissue. TIMP-1 mRNA was also localised to ovarian follicles throughout the ovarian cycle. Expression occurred in the thecal layer of smaller follicles (< 1.5 mm) and the granulosal layer of larger pre-ovulatory follicles. In atretic follicles, TIMP-1 was highly expressed at the interface between the thecal and granulosal cells. TIMP-1 was found to be predominantly expressed in steroidogenic tissues, particularly the ovary, adrenal and placenta. These data support a role for changes in TIMP-1 expression in tissue remodelling in the ovary and are consistent with an additional function of TIMP-1 as a facilitator of steroidogenesis.

Luteinizing hormone receptor in the human corpus luteum: lack of down-regulation during maternal recognition of pregnancy

Luteal progesterone production is dependent on luteinizing hormone (LH) from the pituitary gland. Despite continuing LH secretion, the human corpus luteum undergoes functional luteolysis unless it is 'rescued' by human chorionic gonadotrophin (HCG), produced by the implanting blastocyst. As LH and HCG act through a common receptor, this study sought to determine the expression of the LH/ HCG receptor in the corpus luteum during maternal recognition of pregnancy. Corpora lutea were collected at hysterectomy from women in the normal luteal phase and after luteal 'rescue' with exogenous HCG. In each case the corpus luteum was classified according to the date of the LH surge measured in daily urine samples. The expression of the LH receptor was investigated by Northern blotting, in-situ hybridization and in-situ ligand binding. LH receptor mRNA and ligand binding activity were detected in corpora lutea from all stages of the luteal phase. LH receptor expression and binding were maintained during maternal recognition of pregnancy in the presence of exponentially increasing HCG concentrations. These data show that the LH receptor is maintained throughout the functional life-span of the human corpus luteum and is not down-regulated during maternal recognition of pregnancy.

Serum inhibin B levels reflect Sertoli cell function in normal men and men with testicular dysfunction

We used a recently developed ELISA format to test the hypothesis that inhibin B is the physiologically active form of inhibin in men. We measured and compared inhibin A, inhibin B, and pro-alpha-C-related immunoreactive peptides (pro-alpha-C-RI) in normal men before and after perturbations of their gonadotropin levels and baseline values in normal men and men with various disturbances of the hypothalamic-pituitary-testicular axis including men with idiopathic hypogonadotropic hypogonadism, infertile men with elevated FSH, men with Klinefelter's syndrome, and orchidectomized men. Mean serum inhibin concentrations were significantly higher in normal men than untreated men with idiopathic hypogonadotropic hypogonadism, infertile men with elevated FSH, untreated men with Klinefelter's syndrome, and orchidectomized men (187 +/- 28 vs 45 +/- 11, 37 +/- 6, 11 +/- 3, and < or = 10 pg/mL, respectively; P < 0.05). Inhibin B levels were below the limit of detection in all of the orchidectomized men. Pro-alpha-C-RI levels were detectable in all men studied including the orchidectomized men, and no significant differences in the pro-alpha-C-RI levels were noted between the normal men and men with various testicular diseases were noted except that orchidectomized men had significantly lower pro-alpha-C-RI levels than all other groups (P < 0.05). Inhibin A was undetectable in all men tested in this study. Six normal men who were administered exogenous levonorgestrel and testosterone had significantly lower serum gonadotropin, inhibin B, and pro-alpha-C-RI levels during the treatment period than the control and recovery periods (P < 0.05). Ten normal men who were administered human recombinant FSH had significantly higher peak serum FSH (21.85 +/- 3.23 IU/L vs. 3.01 +/- 0.51 IU/L), inhibin B (311 +/- 88 pg/mL vs. 151 +/- 23 pg/mL) and pro-alpha-C-RI (646 +/- 69 vs. 402 +/- 38 pg/mL) levels during the treatment period than the baseline values (P < 0.05). We conclude that inhibin B is a unique testicular product that is not detectable in the sera of orchidectomized men, is responsive to FSH stimulation, and has a reciprocal relationship with serum FSH levels in men with various forms of testicular disease. Therefore, inhibin B is likely to be the physiologically important form of inhibin in men.

Decreased inhibin B secretion is associated with the monotropic FSH rise in older, ovulatory women: a study of serum and follicular fluid levels of dimeric inhibin A and B in spontaneous menstrual cycles

This study sought to compare circulating and follicular fluid (FF) concentrations of dimeric inhibin A and B utilizing specific two-site ELISAs for these hormones in normal older and younger ovulatory women. METHODS. Normally ovulating women age 40-45 (n = 10) and 20-25 (n = 13) were studied throughout the follicular phase with daily blood sampling, transvaginal ultrasound examinations, and dominant follicle aspiration. When the dominant follicle reached a mean diameter of 16 mm or serum estradiol (E2) was > or = 550 pmol/L, 10,000 IU of hCG was administered intramuscularly followed 32 hours later by transvaginal follicle aspiration. Serum and FF samples were analyzed for E2, FSH, and inhibin A and B. Daily hormone levels were compared by ANOVA, and mean results were compared using t-tests.

RESULTS

Older women developed a dominant follicle sooner, meeting criteria for hCG cycle day 10.6 +/- 0.4 vs. 14.5 +/- 1.0 p < 0.001. As expected, the older group had higher maximal serum FSH concentrations compared to the younger women (11.4 +/- 0.5 vs. 8.0 +/- 0.4 IU/L, p < 0.001). We compared hormone concentrations from days-1 to 3 (where day 0 = day of maximal FSH concentration). E2 concentration was higher in the older women (p = 0.002), and there was no significant difference in inhibin A secretion (p = 0.61). In contrast, mean inhibin B concentration was significantly lower in the older women (p = 0.04). On the day of aspiration of the dominant follicle, serum inhibin B was decreased in the older subjects (42.6 +/- 6.5 vs. 153.1 +/- 53 pg/ml, p = 0.02), whereas older subjects had higher levels of inhibin A (106 +/- 16 vs. 60.4 +/- 9.4 pg/ml, p = 0.04) and similar E2 levels (665 +/- 35.2 vs. 687 +/- 92 pmol/L, p = 0.83). There were no differences in FF concentrations of inhibin B (164 +/- 31 vs. 174 +/- 37 ng/ml, p = 0.85), inhibin A (317.7 +/- 38 vs. 248 +/- 57 ng/ml, p = 0.16), or E2 (2074 +/- 294 vs. 2474 +/- 338 nmol/L, p = 0.82) in the older and younger women. CONCLUSION. Follicular phase inhibin B secretion is decreased in older ovulatory women who demonstrate a monotropic FSH rise, whereas inhibin A secretion is similar to that in younger women. The dominant follicle in these older women appears to be normal in terms of FF E2 and inhibin content. We speculate that decreased inhibin B secretion most likely reflects a diminished follicular pool in older women and may be an important regulator of the monotropic FSH rise.

Inhibin-B: a likely candidate for the physiologically important form of inhibin in men

Inhibin is a glycoprotein hormone that is defined on the basis of inhibition of pituitary FSH production, However, previous data have not shown any correlation between RIA measurements of inhibin and FSH in men. New enzyme-linked immunosorbent assays, specific for inhibin A, inhibin B, and inhibin pro-alphaC-related immunoreactivity, were applied to the measurement of inhibin in 32 healthy men. Further measurements of inhibin B and pro-alphaC-RI were carried out on groups of men exhibiting a wide range of FSH concentrations, including semen donors, infertile men, and men with elevated FSH concentrations. Inhibin A was undetectable (<2 pg/mL) in all men studied. The healthy men studied all had measurable concentrations of inhibin B (135.6 pg/mL; confidence interval, 108.4-169.4) and pro-alphaC-RI (426.3 pg/mL; confidence interval, 378.4-480.2). A close negative correlation was found between the inhibin B and FSH concentrations in the semen donors (r = -0.69; P < 0.001), the infertile men (r = -0.81; P < 0.001), and the men with elevated FSH concentrations (r = -0.54; P < 0.01), but not in a group of healthy volunteers (r = -0.08; P = NS). No correlation was observed between concentrations of pro-alphaC-RI and FSH in any of the groups studied. These results strongly suggest that the physiologically important form of inhibin in men is inhibin B, which has a critical effect on FSH release. Inhibin B may offer a clinically useful serum marker of testicular function.

Measurement of circulating inhibin forms during the establishment of pregnancy

This study investigated the forms of inhibin released into the circulation 1) in very early pregnancy, 2) after stimulation of the corpus luteum by exogenous hCG, and 3) in abnormal and failing human pregnancy. Samples were assayed by enzyme-linked immunosorbent assays for inhibin A, inhibin B, and inhibin pro-alphaC-related immunoreactivity (pro-alphaC-RI). The concentration of inhibin A rose steadily during the conception luteal phase to an initial peak 12 days after ovulation (104 +/- 23 pg/mL), then rose rapidly to a further peak 43 days after ovulation 424 +/- 6 pg/mL). The concentration of pro-alphaC-RI exhibited a much larger peak on day 15 after ovulation (1423 +/- 361 pg/mL), but fell thereafter. The concentration of inhibin B was low after ovulation and subsequently barely detectable in pregnancy. hCG treatment resulted in a significant rise in the concentrations of inhibin A and pro-alphaC-RI, but had no effect on the inhibin B concentration. The pro-alphaC-RI concentration was a better indicator of continuing pregnancy viability than either hCG or inhibin A. Early trophoblast secretes proportionately more bioactive inhibin than the corpus luteum. The corpus luteum and trophoblast do not secrete inhibin B into the circulation. These data support the concept of different physiological roles for different inhibin forms.

Measurement of dimeric inhibin B throughout the human menstrual cycle

This report describes the development of a specific and sensitive assay for inhibin B and its application to the measurement of inhibin B concentrations in plasma during the human menstrual cycle. A monoclonal antibody raised against a synthetic peptide from the betaB-subunit was combined with an antibody to an inhibin alpha-subunit sequence in a double antibody enzyme-linked immunosorbent assay format. The validated assay had a limit of detection of 10 pg/mL and 0.5% cross-reactivity with inhibin A. Using this immunoassay, we found that the plasma concentration of inhibin B rose rapidly in the early follicular phase to a peak of 85.2 +/- 9.6 pg/mL on the day after the intercycle FSH rise, then fell progressively during the remainder of the follicular phase. Two days after the midcycle LH peak, there was a short lived peak in the inhibin B concentration (133.6 +/- 31.2 pg/mL), which then fell to a low concentration (<20 pg/mL) for the remainder of the luteal phase. In contrast, the inhibin A concentration was low in the early follicular phase, rose at ovulation, and was maximal during the midluteal phase. The concentration of inhibin B in individual follicular fluid samples was 20- to 200-fold higher than the concentration of inhibin A and was highest in follicular fluid samples from the early follicular phase. Inhibin B appears to be the predominant form of inhibin in the preovulatory follicle. The different patterns of circulating inhibin B and inhibin A concentrations observed during the human menstrual cycle suggest that these forms may have different physiological roles.

GnRH receptor mRNA expression by in-situ hybridization in the primate pituitary and ovary

Gonadotrophin-releasing hormone (GnRH) receptors are present on the ovary as well as in the anterior pituitary gland. GnRH analogues may exert their actions in part via these ovarian receptors. However, in the primate ovary, GnRH receptors are of low affinity and their significance is questionable. The aim of the present study was to compare pituitary and ovarian expression of the GnRH receptor mRNA by in-situ hybridization to gain further information on the possible significance of the ovarian receptor. Pituitaries and ovaries were obtained from two stump-tailed macaque monkeys and three marmoset monkeys at the mid-luteal phase of the ovulatory cycle. Human corpora lutea were obtained during the early and mid-luteal phase and after 'rescue' by human chorionic gonadotrophin (HCG) and a whole ovary obtained during the late luteal phase (n = 1 per group). Frozen tissue sections were incubated with a 33P-labelled probe to the human GnRH receptor and exposed for 4 weeks. All pituitary glands exhibited intense silver grains in the anterior pituitary gland. In the ovaries, grains were present at low levels in the granulosa cells of antral follicles, just above tissue background in corpora lutea and indistinguishable from tissue background in the remaining ovarian compartments. These results demonstrate that the GnRH receptor mRNA in the primate pituitary is present in sufficient quantities to be clearly detectable in the anterior pituitary gland by in-situ hybridization. In contrast, in the human and monkey, ovary levels of mRNA appear to be very low.

Expression of tissue inhibitor of metalloproteinases-1 in the human corpus luteum after luteal rescue

Tissue inhibitor of metalloproteinases-1 (TIMP-1) is a specific inhibitor of a group of proteolytic enzymes known as matrix metalloproteinases. These enzymes have been widely implicated in the process of tissue remodelling. Extensive remodelling occurs in the corpus luteum during luteolysis unless human chorionic gonadotrophin (hCG) is produced by the early conceptus. This study aimed to investigate the expression and localisation of TIMP-1 in human corpora lutea during the luteal phase of the cycle and after luteal rescue with exogenous hCG to mimic the changes of early pregnancy. Human corpora lutea from the early (n = 4), mid- (n = 4) and late (n = 4) luteal phases and after luteal rescue by hCG (n = 4) were obtained at the time of hysterectomy. Expression of TIMP-1 was investigated in these tissues by Western blotting, immunohistochemistry, Northern blotting and in situ hybridisation. Luteal cells of thecal origin were distinguished from those of granulosa origin by immunostaining for 17 alpha-hydroxylase. A 30 kDa protein consistent with TIMP-1 was detected in human corpora lutea. This protein was localised to the granulosa lutein cells in all tissues examined. TIMP-1 mRNA was found in large quantities in all glands examined and this again localised to the granulosa lutein cells. The expression and localisation of TIMP-1 did not change throughout the luteal phase and was not altered by luteal rescue. The function of this uniform expression of TIMP-1 in the corpus luteum is not clear but these data suggest that the inhibition of structural luteolysis during maternal recognition of pregnancy is not mediated by regulation of TIMP-1 expression.

Quantification of inhibin pro-alpha C-containing forms in human serum by a new ultrasensitive two-site enzyme-linked immunosorbent assay

Precursor forms of the alpha-subunit of inhibin are abundant in human follicular fluid and possibly plasma, although their function is uncertain. We now describe the development of a new enzyme-linked immunosorbent assay to measure inhibin forms containing both the pro and alpha C regions of the alpha-subunit. The assay has a detection limit for purified human pro-alpha C of 0.5 pg/mL and less than 0.02% cross-reaction with recombinant forms of inhibin, activin, and follistatin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting of follicular fluid extracts demonstrated that the assay is likely to detect pro-containing precursor forms of both the free alpha-subunit and intact dimeric inhibin. The serum concentration was measured in normal men (446 +/- 28 pg/mL), postmenopausal women (45.8 +/- 3.8 pg/mL), and women treated with FSH before in vitro fertilization (1827 pg/mL). Pooled human follicular fluid contained 488 ng/mL. The mean serum concentration in the female menstrual cycle rose from 150.6 +/- 26.1 pg/mL in the early follicular phase to 692.2 +/- 113 pg/mL in the midluteal phase. This assay offers a useful tool for investigation of the role of inhibin-related proteins in human reproduction. There may be particular clinical value under circumstances in which other assays for inhibin forms have insufficient sensitivity.

Induced luteal regression in the primate: evidence for apoptosis and changes in c-myc protein

There is increasing molecular evidence that apoptosis is involved in the process of structural luteal regression in non-primate species. Apoptosis is dependent upon the activation of certain proto-oncogenes and c-myc protein has an important regulatory role in this process in some cell types. The aim of the present study was to determine the occurrence and localisation of c-myc protein within the primate corpus luteum, determine changes during induction of luteal regression and examine the corpora lutea for morphological evidence of apoptosis. Ovaries were studied from marmoset monkeys in the late follicular, and in the early, mid and late luteal phases. Luteal regression was induced either by treatment with prostaglandin F2 alpha analogue or GnRH antagonist administered during the mid luteal phase and ovaries obtained 24 and 48 h later. Immunocytochemistry was performed using a monoclonal antibody to the c-myc protein. In pre-ovulatory follicles positive staining was found in the nucleus of a few granulosal cells and in the cytoplasm of thecal cells. c-myc was present in all corpora lutea where it was localised predominantly in the cytoplasm. In early corpora lutea, scattered cells with intense staining were observed in the presence of a majority of moderately or weakly stained cells. In the mid and late luteal phases, corpora lutea were uniformly moderately stained for c-myc. Following induction of luteal regression, regression, nuclear degeneration with condensation and fragmentation indicative of apoptosis was observed. In other luteal cells, increased membranes suggested necrosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Low dose transdermal oestradiol suppresses gonadotrophin secretion in breast-feeding women

The object of the study was to investigate the effect on gonadotrophin secretion of a small increase in oestradiol concentration. A total of 13 fully breast-feeding women (12 weeks post-partum) underwent serial blood sampling at 10 min intervals for 12 h on 2 different days; day 1 untreated and day 5 after 3 days of treatment with transcutaneous oestradiol (100 micrograms/day). On both days bolus gonadotrophin-releasing hormone (GnRH; 10 micrograms i.v.) was given after a 10 h baseline period. In six of the subjects, a naloxone infusion was administered during the second study day. Application of transdermal oestradiol raised the oestradiol concentration within the normal follicular phase range. The mean luteinizing hormone (LH) concentration on day 5 was found to be significantly lower than that on day 1 (P < 0.05). The LH response to GnRH was, however, significantly higher on day 5 than day 1 (P < 0.001). The mean follicle stimulating hormone (FSH) concentration on day 5 was also significantly lower than that on day 1 (P < 0.01), while the peak concentration after GnRH was unchanged. When the opioid antagonist naloxone was infused after oestradiol treatment, the subjects with low pre-study oestradiol concentrations exhibited no effect on LH concentration, while in the subjects with higher oestradiol concentrations the LH concentration was increased. It was concluded that the administration of small doses of oestradiol caused a significant fall in gonadotrophin concentration in breast-feeding women.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunolocalization of bcl-2 protein in human endometrium in the menstrual cycle and simulated early pregnancy

Cell death by apoptosis is now regarded as an important feature of normal endometrial physiology. Recent reports have suggested that bcl-2, a proto-oncogene responsible for the suppression of apoptosis, is expressed in endometrium and may be involved in the regulation of menstruation. Using standard immunohistochemical procedures, the immunoreactivity of bcl-2 and progesterone receptors has been investigated in normal human endometrium throughout the menstrual cycle (n = 25) as well as endometrium exposed to continued oestradiol and progesterone stimulation by 'rescue' of corpus luteum (n = 4) with exogenous human chorionic gonadotrophin (HCG) administration (pseudopregnancy). Marked immunoreactivity, consistent with previous reports, was noted in the glandular epithelium during the proliferative phase of the cycle. Immunostaining persisted in the glandular epithelium during the secretory phase, although the percentage and intensity of staining was markedly reduced. Staining in the stromal compartment was only noted during the late secretory phase of the cycle. Co-localization with an antibody against CD56 demonstrated that this immunoactivity largely reflected the presence of lymphocytes in the stroma. Endometrium from subjects who underwent 'luteal rescue' displayed limited immunostaining in either glands or stroma. The absence of significant bcl-2 expression in endocrinologically maintained endometrium makes it highly unlikely that bcl-2 is important in prolonging endometrial cell survival in the luteal phase of the menstrual cycle.

Immunolocalization of bcl-2 in the human corpus luteum

The mechanisms of luteal regression and rescue in women are unknown but forms of programmed cell death may be involved. The proto-oncogene bcl-2 is an important inhibitor of apoptosis but has not previously been described in the human corpus luteum. Immunohistochemical localization of bcl-2 protein was investigated in human corpora lutea obtained from women undergoing surgery during endocrine monitored menstrual cycles as well as from women who had been treated with human chorionic gonadotrophin (HCG) to prolong the luteal phase. Bcl-2 was found to be localized in granulosa-lutein, theca-lutein (as identified by co-localization of P450(17)alpha-hydroxylase) and the endothelial cells around some blood vessels. Immunoblotting demonstrated the presence of a single band of approximately MW 26 kDa. There was no apparent change in either the intensity of immunostaining or the histological localization during the normal luteal phase or following treatment with human chorionic gonadotrophin. The product of the proto-oncogene bcl-2 is present in the human corpus luteum. It is unlikely that bcl-2 expression alone is responsible for prolongation of the lifespan of the corpus luteum in early pregnancy although it is possible that the action of the bcl-2 gene present is modified by changes in other members of the bcl-2 family.

Measurement of creatine kinase activity and diagnosis of ectopic pregnancy

OBJECTIVE

To investigate whether the measurement of maternal plasma creatine kinase concentration is of clinical value in the diagnosis of tubal ectopic pregnancy.

DESIGN

A retrospective observational study covering a three month period.

SETTING

The gynaecological emergency service of a UK teaching hospital.

SUBJECTS

One hundred and twenty women presenting with clinical suspicion of an ectopic pregnancy such that plasma human chorionic gonadotrophin (hCG) concentration was measured.

MAIN OUTCOME MEASURES

Plasma hCG and creatine kinase concentrations were measured. Pregnancies were classified as ectopic pregnancy, complete miscarriage, incomplete miscarriage or ongoing pregnancy. Pregnancies were further classified as uncertain diagnosis if the diagnosis was not clear after initial investigation.

RESULTS

Twenty-one of the patients had an ectopic pregnancy. Diagnosis was classified as uncertain in 48% of pregnancies studied and in 54% of ectopic pregnancies during the study period. The mean plasma creatine kinase was higher in ectopic pregnancies than other pregnancies in the study group (P < 0.01) and remained higher in the subgroup of patients with uncertain diagnosis (P < 0.05) but there were significant overlaps in creatine kinase concentrations in all four clinical groups. When a cut-off point of 45 iu/l is used, the measurement of plasma creatine kinase activity has a sensitivity of 0.57 and a specificity of 0.67 for the diagnosis of ectopic pregnancy.

Detection of dimeric inhibin throughout the human menstrual cycle by two-site enzyme immunoassay

OBJECTIVE

We have developed and validated a two-site immunoassay for the measurement of dimeric inhibin in plasma and subsequently measured dimeric inhibin levels in plasma through the normal female menstrual cycle.

DESIGN

Recombinant inhibin added to plasma samples was quantitatively recovered in both follicular and luteal phase, and serial dilutions of samples were tested for parallelism to similar dilutions of recombinant 32 kDa inhibin. Daily samples were assayed from four women through a menstrual cycle.

PATIENTS

(a) Four groups of six women who (i) were in the follicular phase of a normal menstrual cycle, (ii) were in the luteal phase of a normal menstrual cycle, (iii) were post-menopausal and (iV) who had received hMG to induce superovulation. (b) Four healthy female volunteers aged 25-33.

RESULTS

Post-menopausal women had less than 2 ng/l of inhibin whereas six women treated with hMG had dimeric inhibin concentrations up to 1125 ng/l. During the early follicular phase, at the time of onset of menstruation, extremely low levels of dimeric inhibin were found (3.4 ng/l (CI 2.2-5.0)) while in the late follicular phase, there was a marked increase in dimeric inhibin concentration. The concentration of dimeric inhibin was maximal (65.6 ng/l (CI 53.1-81.1)) in the mid-luteal phase. The overall pattern of dimeric inhibin concentration during the menstrual cycle was similar to that observed with previous inhibin assays although the magnitude of change was considerably greater.

CONCLUSION

The human ovary, in particular the corpus luteum, secretes significant amounts of dimeric and therefore biologically active inhibin.

Abnormal twenty-four hour pattern of pulsatile luteinizing hormone secretion and the response to naloxone in women with hyperprolactinaemic amenorrhoea

OBJECTIVE

Hyperprolactinaemic amenorrhoea is associated with disturbances of pulsatile gonadotrophin secretion. The underlying mechanism remains unclear and the aim of this study was to investigate the 24-hour secretory pattern of gonadotrophins in women with hyperprolactinaemic amenorrhoea. The effect of opioid blockade using naloxone infusion on LH secretory pattern was also studied.

DESIGN

The secretory patterns of LH, FSH, PRL and their responses to naloxone infusion were studied by serial blood samples collected at 10-minute intervals for 24 hours. On the following day, naloxone was infused at a dose of 1.6 mg per hour for 4 hours.

PATIENTS

Eight women with hyperprolactinaemic amenorrhoea, two women hyperprolactinaemic but with normal ovarian cycles, and nine control subjects in the early follicular phase of menstrual cycle.

MEASUREMENTS

Concentrations of LH, FSH and PRL were measured in plasma samples obtained at 10-minute intervals for 24 hours. In one woman, concentrations of urinary oestrone glucuronide were measured daily during treatment with pulsatile GnRH.

RESULTS

The number of LH pulses per 24 hours was significantly fewer in women with hyperprolactinaemic amenorrhoea than in those with hyperprolactinaemia with normal cycles or control subjects (mean +/- SEM 4.5 +/- 2.4 vs 13.5 +/- 2.5 vs 17.3 +/- 0.8, P < 0.001). The magnitude of each episode of secretion was significantly higher in the hyperprolactinaemic amenorrhoeic women (P < 0.05) so the overall mean concentrations of LH throughout the 24-hour period was similar in the three groups (5.2 +/- 1.1, 4.8 +/- 0.8 and 5.2 +/- 0.4 U/l respectively). In women with hyperprolactinaemic amenorrhoea there was no significant change in the pattern of LH secretion during sleep in contrast to the control women in whom there was a slowing in the LH pulse frequency during the night. There was no significant change in the mean concentrations of LH, FSH and PRL during the naloxone infusion. There were also no significant changes in the LH pulse frequency in response to naloxone infusion when compared with an equivalent period of time in the previous 24 hours. In one hyperprolactinaemic amenorrhoeic woman, follicular development, ovulation and pregnancy were induced when gonadotrophin releasing hormone (GnRH) was infused in a pulsatile manner at a dose of 5 micrograms every 90 minutes.

CONCLUSIONS

The suppression of normal ovarian cycles in women with hyperprolactinaemic amenorrhoea is due to a significant reduction in frequency of LH (GnRH) secretion which is not due to an increase in hypothalamic opioid activity. As normal ovarian cycles can occur or be induced by exogenous GnRH in hyperprolactinaemia, it is unlikely that a high level of prolactin by itself inhibits follicular development and ovulation.

The relationship between peripheral immunoactive inhibin, human chorionic gonadotrophin, oestradiol and progesterone during human pregnancy

OBJECTIVE

The objective of this study was to investigate serial changes in the plasma concentration of inhibin in both the very early days of pregnancy following implantation and in late pregnancy. The timing of the changes in inhibin concentration relative to changes in the concentrations of other hormones of pregnancy was also investigated.

DESIGN

Serial observations of the peripheral concentrations of inhibin and other hormones in two groups of healthy volunteers in (a) early pregnancy and (b) late pregnancy.

PATIENTS

(a) Four healthy women recruited on cessation of contraception prior to conception. (b) Nine healthy women recruited at the antenatal clinic.

MEASUREMENTS

In the early pregnancy subjects, the concentrations of inhibin, progesterone, oestradiol and hCG were measured in plasma samples obtained three times per week from day 8 to day 10 of each menstrual cycle until 11 weeks after the last menstrual period in the conception cycle. In the late pregnancy subjects, plasma samples were obtained at 4-week intervals from 12 weeks until term.

RESULTS

The concentration of inhibin, progesterone and oestradiol in conception cycles were similar to those in the preceding cycles until the mid/to late-luteal phase of the cycle when hCG was first measureable. By day 12 of the luteal phase the concentration of inhibin was significantly higher in the pregnancy cycle than in the non-pregnancy cycle (P < 0.05) and progressively increased after the time of the missed menstrual period. The concentration of inhibin reached a peak (513.0 U/l, CI 442.1-595.3) by day 47 when the concentration of hCG was maximal. In early pregnancy the concentration of inhibin was correlated with that of hCG (r = 0.361; P < 0.01) as well as progesterone (r = 0.584, P < 0.001) and oestradiol (r = 0.602, P < 0.001). After 12 weeks there was no significant correlation between hCG and inhibin although significant correlations persisted with progesterone (r = 0.553, P < 0.001) and oestradiol (r = 0.361, P < 0.01).

CONCLUSIONS

The corpus luteum makes a significant contribution to the production of inhibin in early pregnancy while after 12 weeks the placenta is the major source.

The source of inhibin secretion during the human menstrual cycle

The source of inhibin secretion during the human menstrual cycle was investigated in two ways. The concentration of inhibin was compared in samples obtained from the ovarian and peripheral veins of 41 women undergoing hysterectomy. In 13 of the women, the corpus luteum was enucleated at operation and the peripheral concentration of inhibin measured at intervals for 24 h. Inhibin was assayed by a heterologous RIA using an antiserum raised against 31 kilodalton bovine inhibin. The concentrations of estradiol and progesterone in the peripheral and ovarian veins were similar to those previously reported. During the early follicular phase, the geometric mean inhibin concentrations were found to be significantly higher in both the right and left ovarian veins than the peripheral vein (180.4 and 157.7 vs. 78.7 U/L: P less than 0.02) but no difference was found in the late follicular phase between the vein draining the dominant ovary and the contralateral ovarian vein (231.1 vs. 193.4 U/L: NS). The inhibin concentrations in the veins draining the ovary bearing a corpus luteum were, however, significantly higher than those in the contralateral ovarian veins during the mid (409.1 vs. 203.6 U/L: P less than 0.02) and late (287.1 vs. 153.2 U/L: P less than 0.01) luteal phases. After enucleation of the corpus luteum, the inhibin concentration fell from the level seen before lutectomy (134.4 U/L) to 80.0 U/L at 24 h (P less than 0.01). This study demonstrates conclusively that the human corpus luteum secretes inhibin. No increase in inhibin secretion was seen from the dominant follicle in the late follicular phase. This casts doubt on the hypothesis that the selective suppression of FSH during the follicular phase is due to inhibin from the dominant follicle.

Effect of recombinant activin on androgen synthesis in cultured human thecal cells

The effect of activin-A on ovarian androgen synthesis was tested in vitro using serum-free monolayer cultures of human thecal cells. Maximal rates of androgen (androstenedione and dehydroepiandrosterone) production were induced by treating the cells for 4 days with LH (10 ng/mL) in the presence of insulin-like growth factor-I (greater than or equal to 30 ng/mL). The additional presence of recombinant activin-A (1-100 ng/mL) in culture medium caused dose-dependent suppression of thecal cell androgen production, with 50% maximal inhibition occurring at an activin-A concentration of about 10 ng/mL. Progesterone production was only suppressed by high dose (100 ng/mL) activin-A, and inhibition of steroid production occurred without inhibition of DNA synthesis (tritiated thymidine uptake). These results reveal a potent and selective inhibitory action of activin-A on thecal cell androgen synthesis, consistent with a paracrine function for activin(s) in modulating follicular androgen biosynthesis in the human ovary.

Immunocytochemical localization of inhibin alpha-subunit in the human corpus luteum

The localization of inhibin alpha-subunit within the human corpus luteum was investigated. The antiserum used was raised in sheep against the first 1-23 amino acid sequence of the N-terminus of the human inhibin alpha-subunit. Using the avidin-biotin immunoperoxidase technique, intense immunostaining was localized within the granulosa-lutein cells of the corpus luteum, with absence of staining in the theca-lutein cells and surrounding ovarian tissue. Similar distribution of inhibin alpha-subunit immunostaining was observed in 12 corpora lutea obtained during the early, mid- and late-luteal phases and no changes in intensity were apparent at these different stages. Negative controls were obtained by applying antiserum which had been preabsorbed overnight with excess inhibin peptide in place of primary antiserum and also normal nonimmune sheep serum as a substitute for primary antiserum. These results provide further evidence that the human corpus luteum is a significant source of immunoreactive inhibin during the normal human menstrual cycle. The specific localization within the granulosalutein cells of the corpus luteum suggests that inhibin alpha-subunit production may originate from a discrete cell population within the human corpus luteum.

Effect of recombinant inhibin on androgen synthesis in cultured human thecal cells

Effects of inhibin (recombinant human inhibin-A) on ovarian androgen synthesis were tested in vitro using serum-free monolayer cultures of human thecal cells. Treatment for 4 days with inhibin alone at doses between 10 and 100 ng/ml caused modest (approximately 2-fold) increases in production of androgen (androstenedione and dehydroepiandrosterone): similar to the maximal level of stimulation caused by luteinizing hormone (LH) (10 ng/ml) alone but only about one-third of that caused by insulin-like growth factor I (IGF-I) (30 ng/ml) alone. Combined treatment with LH and inhibin elicited additive effects on androgen production whereas LH and IGF-I were synergistic, giving rise to androgen production rates at least 40 times greater than control. Additional presence of inhibin caused up to 10-fold augmentation of the response to LH + IGF-I. Activin (recombinant human activin-A) was previously shown to inhibit LH + IGF-I-induced androgen synthesis in this human thecal cell culture system. In the present study we found that the additional presence of inhibin (greater than 1 ng/ml) completely neutralized this inhibitory action of activin (10 ng/ml). These effects of inhibin were dose-dependent (ED50 1-10 ng/ml) and maximal at approximately 100 ng/ml. Inhibin stimulation of androgen synthesis occurred in the absence of measurable effects on progesterone production, and cell numbers in cultured cell monolayers were unaltered by the protein. It is concluded that inhibin exerts potent and selective stimulation of human thecal cell androgen synthesis in vitro. These results a paracrine role for inhibin(s) in modulating follicular androgen biosynthesis in the human ovary.

Pharmacological 'rescue' of the corpus luteum results in increased inhibin production

Inhibin production by the corpus luteum was investigated by undertaking pharmacological rescue of the corpus luteum with hCG in four healthy women. Blood samples were collected daily for two menstrual cycles. Starting 7 days after the LH surge in the second cycle, incremental doses of hCG (125-8000 IU) were administered daily for 7 days resulting in hCG levels comparable to those seen in normal pregnancy. Following hCG, the luteal phase was prolonged and there were significant increases in the plasma concentrations of inhibin (P less than 0.05), and oestradiol (P less than 0.05). The progesterone concentration was maintained at the mid-luteal phase peak and as a result was significantly higher than those on the equivalent days of the control cycle (P less than 0.05). It was concluded that rescue of the corpus luteum with physiological levels of hCG resulted in a significant output of inhibin, thus suggesting that the corpus luteum is a significant source of inhibin in early pregnancy.

Reduction in postprandial energy expenditure during pregnancy

Energy expenditure was measured during pregnancy in seven primigravid women at 12-15, 25-28, and 34-36 weeks and after the cessation of lactation. On each occasion the resting metabolic rate and the increase in metabolic rate after ingestion of a liquid test meal were measured by indirect calorimetry. In absolute terms the resting metabolic rate increased steadily during pregnancy but when expressed per unit of body weight no change was found. The energetic response to a mixed constituent meal was significantly reduced by 28% in the middle trimester of pregnancy. These findings suggest a possible maternal adaptation to increase energetic efficiency at a time when the energy demands of the fetus are high.

Diminution in energy expenditure during lactation

Energy expenditure at rest and in response to a meal and to an infusion of noradrenaline was measured in 12 lactating women and compared with that in seven bottle feeding women and seven non-pregnant, non-lactating controls. The energy response of the lactating women was remeasured after lactation stopped. During lactation the resting metabolic rate was unaltered but there was a reduced response to infusion of noradrenaline and to a meal, which increased to normal control values after lactation stopped. Such reductions in expenditure were not found in women who had been bottle feeding and were tested at a similar six to eight weeks post partum. These findings suggest that metabolic efficiency is enhanced in lactating women, who may not need to increase energy intake to the extent suggested by current recommended dietary allowances.