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Background: Choriogonadotropin (CG) beta (FE 999302), a novel recombinant human (h)CG produced by a human cell line, has a longer half-life and higher potency than CG alfa produced by a Chinese hamster ovary cell line. hCG augments steroid production, but the extent of which CG beta treatment during ovarian stimulation (OS) increases steroidogenesis is unknown., Objective: To explore how increasing doses of CG beta during OS augment follicular steroidogenesis and change gene expression in cumulus cells., Study Design: This study is part of a randomized, double-blind, placebo-controlled trial to investigate the efficacy and safety of CG beta plus recombinant follicle-stimulating hormone (rFSH) in women undergoing OS during a long gonadotrophin-releasing hormone agonist protocol. The study primary endpoint was intrafollicular steroid concentrations after CG beta administration. Secondary outcomes were gene expression of FSHR , LHR , CYP19a1 , and androgen receptor ( AR )., Participants/methods: 619 women with anti-Müllerian hormone levels 5-35 pmol/L were randomized to receive placebo or 1, 2, 4, 8, or 12 µg/day CG beta from Day 1 of OS plus rFSH. Follicular fluid (FF) (n=558), granulosa (n=498) and cumulus cells (n=368) were collected at oocyte retrieval. Steroid FF hormones were measured using enzyme-linked immunosorbent assays, gene expression was analyzed in cumulus cells by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and single nucleotide polymorphism (SNP) analysis was performed in granulosa cells., Results: 17-OH-progesterone, androstenedione, testosterone, and estradiol concentrations significantly increased in a CG-beta dose-dependent manner during OS (p<0.0001), reaching up to 10 times higher values in the highest dose group versus placebo. There was no difference between CG beta dose groups and placebo for progesterone. Expression levels of CYP19a1 increased significantly in the highest dose group of CG beta (p=0.0325) but levels of FSHR , LHR and AR were not affected by CG beta administration. There were no differences between the FSHR (307) or LHR (312) SNP genotypes for dose-dependent effects of CG beta in relation to number of oocytes, intrafollicular steroid hormone levels, or gene expression levels., Conclusions: These results reflect the importance of the combined effect of FSH and hCG/LH during OS on granulosa cell activity, follicle health and potentially oocyte quality., Trial Registration Number: 2017-003810-13 (EudraCT Number)., Trial Registration Date: 21 May 2018., Date of First Patient’s Enrolment: 13 June 2018. Presented at the 38th Annual Meeting of the European Society of Human Reproduction and Embryology, P-567, 2022., Competing Interests: BM and PL are employees of Ferring Pharmaceuticals. CA has received payment for lectures from IBSA, Switzerland, and his laboratory was reimbursed for the analyses performed under this study. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declare that this study received funding from Ferring Pharmaceuticals. The funder was involved in the study design, collection, analysis, interpretation of data, the writing of this article and the decision to submit it for publication, (Copyright © 2022 Bøtkjær, Kristensen, Olesen, Larsson, Mannaerts and Andersen.)

Human ovarian cells are phenotypically very different and are often only available in limited amounts. Despite the fact that reference gene (RG) expression stability has been validated in oocytes and other ovarian cells from several animal species, the suitability of a single universal RG in the different human ovarian cells and tissues has not been determined. The present study aimed to validate the expression stability of five of the most used RGs in human oocytes, cumulus cells, preantral follicles, ovarian medulla, and ovarian cortex tissue. The selected genes were glyceraldehyde 3-phosphate dehydrogenase ( GAPDH ), beta-2-microglobulin ( B2M ), large ribosomal protein P0 ( RPLP0 ), beta-actin ( ACTB ), and peptidylprolyl isomerase A ( PPIA ). Overall, the stability of all RGs differed among ovarian cell types and tissues. NormFinder identified ACTB as the best RG for oocytes and cumulus cells, and B2M for medulla tissue and isolated follicles. The combination of two RGs only marginally increased the stability, indicating that using a single validated RG would be sufficient when the available testing material is limited. For the ovarian cortex, depending on culture conditions, GAPDH or ACTB were found to be the most stable genes. Our results highlight the importance of assessing RGs for each cell type or tissue when performing RT-qPCR analysis.

Anti-Müllerian hormone (AMH) is a member of the TGF-β superfamily produced by follicular granulosa cells (GCs) in women from late gestation to the end of reproductive life. AMH is thought to inhibit aromatase (i.e., CYP19) expression and decrease the conversion of androgens to oestrogens, especially in small antral follicles before dominance is achieved. Thus, AMH acts as a gatekeeper of ovarian steroidogenesis. However, the exact function and processing of AMH has not been fully elucidated. The present study measured and determined AMH isoforms in human follicular fluid (FF) from small antral follicles and in human GCs using four ELISAs, western blot, and immunofluorescence analysis. We evaluated the presence of the following isoforms: full-length AMH precursor (proAMH), cleaved associated AMH (AMH N,C ), N-terminal pro-region (AMH N ), and active C-terminal (AMH C ) AMH. A negative correlation between follicle diameter and the AMH forms was detected. Moreover, western blot analysis detected various AMH forms in both FFs and GCs, which did not match our consensus forms, suggesting an unknown proteolytic processing of AMH. The presence of these new molecular weight isoforms of AMH differs between individual follicles of identical size in the same woman. This study detected several AMH forms in FF and GCs obtained from human small antral follicles, which suggests that intrafollicular processing of AMH is complex and variable. Thus, it may be difficult to develop an antibody-based AMH assay that detects all AMH isoforms. Furthermore, the variability between follicles suggests that designing a recombinant AMH standard will be difficult., Competing Interests: Authors AK and BK were employed by the company Ansh Labs. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Mamsen, Bøtkjær, Kristensen, Pors, Jeppesen, Kumar, Kalra, Ernst and Andersen.)

Women with β -thalassemia (BT) and sickle cell disease (SCD) have a high risk of infertility and premature ovarian insufficiency. Different fertility preserving strategies, including ovarian tissue cryopreservation (OTC) and oocyte cryopreservation has been considered, and healthy babies have been born after successful OTC and transplantation. We evaluated follicle number and follicle health in ovarian tissue from a cohort of BT and SCD patients who underwent OTC before the age of 18 years. Patients undergoing OTC from 2002 to 2019 were included. A total of 14 girls and adolescents with BT and four with SCD, aged 2.8-17.4 years at OTC were included together with a reference group of 43 girls and adolescents with non-anemia diseases considered to have normal ovaries aged 0.6-17.9 years at OTC. Ovarian follicle density was measured in cortex biopsies and compared to the reference group. Expression of proteins associated with follicular health was evaluated using immunohistochemistry. Follicles were detected in the ovarian cortex biopsies from all patients with BT and SCD. The follicle densities were within the 95% prediction interval of the reference group in all cases. A similar expression of six proteins essential for follicular health was detected using immunohistochemistry in BT, SCD, and references. OTC should be considered an option for young girls and adolescents with BT and SCD., Competing Interests: AK and BK were employed by the company Ansh Labs. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Mamsen, Kristensen, Pors, Bøtkjær, Ernst, Macklon, Gook, Kumar, Kalra and Andersen.)

Protein supplements are a billion-dollar industry and the intake of these supplements is increasing, especially among young men. However, little is known about whether consumption of these products affects the reproductive health. The aim of this study was to assess the effect of whey protein supplementation on the sperm quality and reproductive health of male mice. A total of 48 male NMRI mice were fed with either plain tap water or a high dose of whey protein (Whey100, BodyLab) supplemented in the drinking water for 3 months. Mice was individually housed with two female mice for five days and reproductive parameters were assessed. DNA fragmentation index (DFI) was assessed at 0 h and 4 h of in vitro incubation using a sperm DNA integrity test (SDI®-test). No significant differences were detected between the groups in the epididymal sperm count, sperm motility, DFI, oxidation-reduction potential (ORP), serum testosterone, body and seminal vesicles weights, relative testis and epididymal weights, testicular morphology, number of impregnated females, or litter size. No correlation was found between ORP and DFI. These results suggest that the highest recommended human dose of whey protein supplementation do not significantly impair the sperm quality and fertility in male mice., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Study Question: How does the human granulosa cell (GC) transcriptome change during ovulation?, Summary Answer: Two transcriptional peaks were observed at 12 h and at 36 h after induction of ovulation, both dominated by genes and pathways known from the inflammatory system., What Is Known Already: The crosstalk between GCs and the oocyte, which is essential for ovulation and oocyte maturation, can be assessed through transcriptomic profiling of GCs. Detailed transcriptional changes during ovulation have not previously been assessed in humans., Study Design, Size, Duration: This prospective cohort study comprised 50 women undergoing fertility treatment in a standard antagonist protocol at a university hospital-affiliated fertility clinic in 2016-2018., Participants/materials, Setting, Methods: From each woman, one sample of GCs was collected by transvaginal ultrasound-guided follicle aspiration either before or 12 h, 17 h or 32 h after ovulation induction (OI). A second sample was collected at oocyte retrieval, 36 h after OI. Total RNA was isolated from GCs and analyzed by microarray. Gene expression differences between the five time points were assessed by ANOVA with a random factor accounting for the pairing of samples, and seven clusters of protein-coding genes representing distinct expression profiles were identified. These were used as input for subsequent bioinformatic analyses to identify enriched pathways and suggest upstream regulators. Subsets of genes were assessed to explore specific ovulatory functions., Main Results and the Role of Chance: We identified 13 345 differentially expressed transcripts across the five time points (false discovery rate, <0.01) of which 58% were protein-coding genes. Two clusters of mainly downregulated genes represented cell cycle pathways and DNA repair. Upregulated genes showed one peak at 12 h that resembled the initiation of an inflammatory response, and one peak at 36 h that resembled the effector functions of inflammation such as vasodilation, angiogenesis, coagulation, chemotaxis and tissue remodelling. Genes involved in cell-matrix interactions as a part of cytoskeletal rearrangement and cell motility were also upregulated at 36 h. Predicted activated upstream regulators of ovulation included FSH, LH, transforming growth factor B1, tumour necrosis factor, nuclear factor kappa-light-chain-enhancer of activated B cells, coagulation factor 2, fibroblast growth factor 2, interleukin 1 and cortisol, among others. The results confirmed early regulation of several previously described factors in a cascade inducing meiotic resumption and suggested new factors involved in cumulus expansion and follicle rupture through co-regulation with previously described factors., Large Scale Data: The microarray data were deposited to the Gene Expression Omnibus (www.ncbi.nlm.nih.gov/gds/, accession number: GSE133868)., Limitations, Reasons for Caution: The study included women undergoing ovarian stimulation and the findings may therefore differ from a natural cycle. However, the results confirm significant regulation of many well-established ovulatory genes from a series of previous studies such as amphiregulin, epiregulin, tumour necrosis factor alfa induced protein 6, tissue inhibitor of metallopeptidases 1 and plasminogen activator inhibitor 1, which support the relevance of the results., Wider Implications of the Findings: The study increases our understanding of human ovarian function during ovulation, and the publicly available dataset is a valuable resource for future investigations. Suggested upstream regulators and highly differentially expressed genes may be potential pharmaceutical targets in fertility treatment and gynaecology., Study Funding/competing Interest(s): The study was funded by EU Interreg ÔKS V through ReproUnion (www.reprounion.eu) and by a grant from the Region Zealand Research Foundation. None of the authors have any conflicts of interest to declare., (© The Author(s) 2020. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Changes in concentrations of intra-follicular hormones during ovulation are important for final oocyte maturation and endometrial priming to ensure reproductive success. As no human studies have investigated these changes in detail, our objective was to describe the dynamics of major follicular fluid (FF) hormones and transcription of steroidogenic enzymes and steroid receptors in human granulosa cells (GCs) during ovulation. We conducted a prospective cohort study at a public fertility clinic in 2016-2018. Fifty women undergoing ovarian stimulation for fertility treatment were included. From each woman, FF and GCs were collected by transvaginal ultrasound-guided follicle puncture of one follicle at two specific time points during ovulation, and the study covered a total of five time points: before ovulation induction (OI), 12, 17, 32 and 36 h after OI. Follicular fluid concentrations of oestradiol, progesterone, androstenedione, testosterone, 17-hydroxyprogesterone, anti-Mullerian hormone, inhibin A and inhibin B were measured using ELISA assays, and a statistical mixed model was used to analyse differences in hormone levels between time points. Gene expression of 33 steroidogenic enzymes and six hormone receptors in GCs across ovulation were assessed by microarray analysis, and selected genes were validated by quantitative reverse transcription PCR. We found that concentrations of oestradiol, testosterone, progesterone, AMH, inhibin A and inhibin B (P < 0.001) and gene expression of 12 steroidogenic enzymes and five receptors (false discovery rate < 0.0001) changed significantly during ovulation. Furthermore, we found parallel changes in plasma hormones. The substantial changes in follicular hormone production during ovulation highlight their importance for reproductive success., (© The Author(s) 2020. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please e-mail: journals.permission@oup.com.)

Purpose: To evaluate the association between anti-Müllerian hormone (AMH) and follicle density in infertile women with diminished ovarian reserve (DOR) versus women with normal ovarian reserve?, Methods: Case-control study comparing follicle densities in ovarian cortex from 20 infertile women with DOR (AMH ≤ 5 pmol/L) and 100 controls with presumed normal ovarian reserve., Results: For all women > 25 years, the follicle densities correlated positively with AMH levels. For each single picomole per liter increase in AMH the follicle density increased by 6% (95% CI 3.3-8.5%) when adjusted for age. This was similar for women with DOR and controls. The follicle density was 1.8 follicles/mm 3 cortical tissue in women with DOR versus 7.0 in age-paired controls (p = 0.04). The women with DOR had a median AMH of 1.8 pmol/L versus 14.4 pmol/L in the age-paired control group (p < 0.001). The ratio of AMH/follicle density was 1:1 (1.8/1.8) in women with DOR and 2:1 (14.4/7.0) in the age-paired controls. Analyses for gonadotropin receptor polymorphisms could not explain the characteristics of women with DOR. The proportion of secondary follicles was higher in women with DOR compared with controls (4.6% versus 1.4%, p = 0.0003). Pooling all patients, the follicle density decreased significantly by 7.7% for every year added (p < 0.0001). The women with DOR had lower follicle densities than the controls, but the slopes were equal in the two cohorts., Conclusions: Follicle density and AMH concentrations correlate also when AMH is low. However, AMH is only a reliable marker for the true ovarian reserve when age is included in the estimation and women with DOR may have more follicles than their AMH levels imply.

Pregnancy-associated plasma protein-A (PAPP-A) is a key regulator of insulin-like growth factor (IGF) bioactivity, by releasing the IGFs from their corresponding IGF-binding proteins (IGFBPs). The minor allele of the single nucleotide polymorphism (SNP), rs7020782 (serine < tyrosine), in PAPPA has previously been associated with recurrent pregnancy loss as well as with significant reduced levels of PAPP-A protein in human ovarian follicles. The aim of the present study was to reveal a possible functional effect of the rs7020782 SNP in PAPPA by comparing recombinant PAPP-A proteins from transfected human embryonic kidney 293 T cells. The proteolytic cleavage of IGFBP-4 was shown to be affected by the rs7020782 SNP in PAPPA, showing a significantly reduced cleavage rate for the serine variant compared to the tyrosine variant (p-value < 0.001). The serine variant also showed a trend towards reduced cleavage rates, that was not significant, towards IGFBP-2 and IGFBP-5 compared to the tyrosine variant. No differences were found when analysing cell surface binding, complex formation between PAPP-A and STC2 or proMBP, nor when analysing STC1 inhibition of PAPP-A-mediated IGFBP-4 cleavage. Regulation of IGF bioactivity in reproductive tissues is important and the rs7020782 SNP in PAPPA may disturb this regulation by altering the specific activity of PAPP-A.

Purpose: The IGF signaling cascade exerts important regulatory functions in human ovarian folliculogenesis. The scope of this study was to evaluate the transcription profile of insulin-like growth factor (IGF) genes during human ovarian follicle development and to analyze follicle fluid levels of key IGF proteins., Methods: Gene expression profiling was performed with microarray gene analysis. The analysis was assessed from ovarian follicles and granulosa cells (GCs) obtained from isolated stage-specific human ovarian follicles, including preantral follicles, small antral follicles, and preovulatory follicles. Numerous genes involved in the IGF signaling pathway was evaluated and key genes were validated by qPCR from GCs. Protein levels of various IGF components of human follicular fluid (FF) were measured by ELISA and time-resolved immunofluorometric assays (TRIFMA)., Results: The gene expression levels of PAPPA, IGF2, IGF receptors and intracellular IGF-activated genes increased with increasing follicle size. This was especially prominent in the late preovulatory stage where IGF2 expression peaked. Protein levels of intact IGF binding protein-4 decreased significantly in FF from large preovulatory follicles compared with small antral follicles concomitant with higher protein levels of PAPP-A. The IGF modulators IGF-2 receptor, IGFBPs, stanniocalcins, and IGF-2 mRNA binding proteins were all observed to be expressed in the different follicle stages., Conclusions: This study confirms and highlights the importance of PAPP-A regulating bioactive IGF levels throughout folliculogenesis and especially for the high rate of granulosa cell proliferation and expression of key ovarian hormones important in the last part of the follicular phase of the menstrual cycle.

Regulation of human ovarian steroidogenesis differs from other species and precise knowledge on how human small antral follicles (hSAF) develop and acquire competence for continued growth and steroid output is still incomplete. The present study has characterized almost 1,000 normal hSAF collected in connection with cryopreservation of ovarian tissue for fertility preservation. The antral follicles (ranging from 3 to 13 mm) were generally aspirated from one ovary surgically removed during the natural cycle, and the follicular fluid (FF) and the granulosa cells (GC) were isolated and snap-frozen. In FF, the following hormones were measured: inhibin-B, inhibin-A, AMH, follistatin, PAPP-A, estradiol, progesterone, testosterone, and androstenedione. In GC, mRNA gene expressions using q-PCR were measured for the following genes: FSHR, AMH, CYP19 , and AR . All samples in which one of the abovementioned parameters was measured were included, but typically multiple parameters were measured. Highly significant differences in concentration and follicular content in relation to follicular diameter were found for all measured hormones despite massive variability in-between follicles for any given diameter. The results demonstrate that profound changes take place in the hormonal microenvironment around follicular diameters of 8-11 mm corresponding to when follicular selection occurs. At this point, inhibin-B and inhibin-A showed distinct peaks concomitant with a significant reduction in both AMH protein and mRNA expression. Concentrations of inhibins, androgens, FSHR, and AR were intimately associated, and it is suggested that inhibin-B in combination with PAPP-A and thereby IGF2 activity exerts important paracrine signaling at follicular selection. At the same time upregulation of estradiol synthesis and CYP19 mRNA expression increased steroid output profoundly. Furthermore, the highly significant association between FSHR and AR mRNA gene expression enforces important functions of androgens in follicular development. Collectively, these data reintroduce the understanding of the follicular phase as two parted in which regulation of steroidogenesis differs. The profound changes taking place around follicular selection highlight important paracrine actions of TGF-β family members and IGFs for securing dominance of the selected follicle.

Objective: To reveal a possible relationship between two single nucleotide polymorphisms (SNPs) in PAPP-A-1224 (rs7020782) and 327 (rs12375498)-and the level and activity of PAPP-A in follicular fluid (FF) of human small antral follicles, and to analyze the intrafollicular hormone levels., Design: Laboratory investigation., Setting: University hospital., Patient(s): Fifty volunteer women who contributed a total of 210 samples of FF from normal small antral follicles., Intervention(s): Genotyping and measurement of antigen levels of steroids, PAPP-A, stanniocalcin-2 (STC2), and antimüllerian hormone (AMH) plus activity of PAPP-A toward insulin-like growth factor binding protein 4 (IGFBP-4)., Main Outcome Measure(s): Measurement of PAPP-A levels and hormones with enzyme-linked immunosorbent assay (ELISA) and PAPP-A activity toward radiolabeled IGFBP-4., Result(s): Women homozygous for the minor C allele of the 1224 SNP showed a statistically significantly lower level of PAPP-A protein and activity in FF compared with women carrying the major A allele. These women also displayed nonsignificant reduced levels of estradiol and increased levels of AMH and androgen. A statistically significant correlation between FF levels of PAPP-A activity and the molar ratio of PAPP-A/STC2 was obtained. The 327 SNP did not show statistically significant associations., Conclusion(s): This study presents a statistically significant effect of the 1224 SNP on the level and activity of PAPP-A in human follicles, suggesting that the FF level of bioactive insulin-like growth factor depends on the genotype. We observed STC2 to be an important regulator of PAPP-A in human FF. The 1224 SNP has previously been associated with recurrent pregnancy loss, so further evaluation of an underlying mechanism including aberrant control of insulin-like growth factor activity is warranted., (Copyright © 2016 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

Study Question: Is the proteolytic activity of pregnancy-associated plasma protein-A (PAPP-A) regulated by the stanniocalcins (STC1 and STC2) during human follicle maturation?, Summary Answer: The STCs and PAPP-A show similar expression by immunohistochemistry in developing follicles, and regulation of PAPP-A proteolytic activity is suggested by the identification of inhibited protein complexes between PAPP-A and STC1 or STC2 in human follicular fluid (FF)., What Is Known Already: The insulin-like growth factor (IGF)-regulating proteinase PAPP-A is secreted by the granulosa cells of estrogen-dominant follicles and is involved in follicle growth. STC1 and STC2 have recently been identified as novel PAPP-A inhibitors, and their expression in non-human mammalian ovaries has previously been observed., Study Design, Size, Duration: The proteolytic activity of PAPP-A in human follicular fluid was assessed, and the interaction between PAPP-A and the STCs in human ovarian tissues and follicular fluid was analyzed using immunoassays. From 21 women, matched pairs of follicular fluid were obtained from one follicle just prior to final maturation of follicles with human chorionic gonadotrophin (hCG), and from another follicle in connection with oocyte aspiration after hCG treatment. Ovarian tissues were obtained from women having one ovary removed for fertility preservation by cryopreservation prior to gonadotoxic treatment., Participants/materials, Setting, Methods: The concentration and activity of PAPP-A were determined in all samples of follicular fluid. Furthermore, to investigate PAPP-A regulation during follicle development, immunohistochemical staining of PAPP-A, STC1, and STC2 was performed on pre-antral and antral human follicles. To attempt the demonstration of native complexes between PAPP-A and the STCs, immunoprecipitation from a pool of human follicular fluid was performed., Main Results and the Role of Chance: The concentration of PAPP-A antigen in follicular fluid increased upon stimulation of ovulation with hCG (P < 0.02), but at the same time, PAPP-A activity was decreased. PAPP-A, STC1, and STC2 were localized together in primordial, late primary, and antral follicles, indicating that complex formation is possible in ovarian tissue. Covalent PAPP-A:STC2 and non-covalent PAPP-A:STC1 complexes were immunoprecipitated from follicular fluid, documenting for the first time native inhibited complexes between PAPP-A and the STCs., Limitations, Reasons for Caution: We have demonstrated the presence of native complexes between PAPP-A and the STCs in the human ovary, indicating STC-mediated PAPP-A proteolytic inhibition. Further investigation is required to extend this principle to other tissues., Wider Implications of the Findings: Our data suggest that the STCs contribute to PAPP-A regulation during folliculogenesis and support a general model in which STC1 and STC2 are regulators of mammalian IGF activity through inhibition of PAPP-A. We suggest that future functional studies take both PAPP-A and the STCs into consideration., Study Funding/competing Interests: This work was supported by grants from the Novo Nordisk Foundation, and the Danish Council for Independent Research. No competing interests declared., (© The Author 2016. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Objective: To evaluate follicular fluid (FF) levels of pregnancy-associated plasma protein A (PAPP-A) in relation to levels of intrafollicular hormones. Furthermore, immunostaining of human follicles of varying diameters was studied for PAPP-A, antimüllerian hormone (AMH), and aromatase, and the biological activity of PAPP-A in FF was evaluated., Design: Laboratory investigation., Setting: University hospital., Patient(s): A total of 43 women with a total of 80 samples were obtained from three different size-groups of antral follicles collected before and after the LH surge., Intervention(s): ELISA measurement of steroids, PAPP-A, and AMH, immunohistochemistry of PAPP-A, AMH, and aromatase on follicles of different diameter, and proteolytic activity of PAPP-A toward insulin-like growth factor (IGF)-binding protein 4 (IGFBP-4)., Main Outcome Measure(s): Association between FF levels of PAPP-A and measured ovarian hormones, PAPP-A activity in FF, localization of PAPP-A, AMH, and aromatase in antral follicles., Result(s): A highly significant association between FF levels of PAPP-A and all measured hormones were obtained with positive associations toward E2 and P, whereas AMH, T, and A showed strong negative associations. PAPP-A proteolytic activity toward IGFBP-4 was detected in human FF. PAPP-A immunostaining shifted from being primarily present in theca cells of small antral follicles to being expressed in granulosa cells (GCs) of preovulatory follicles. In contrast, AMH expression became reduced with increasing follicular diameter. Aromatase expression was highly specifically localized to GCs of preovulatory follicles., Conclusion(s): The results suggest that PAPP-A is specifically involved in the regulation of steroidogenesis in human antral follicles. Local regulation of IGF-II activity may represent a mechanism by which PAPP-A exerts this function and highlights the importance of IGF signaling during follicular development., (Copyright © 2015 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)