Empty follicular syndrome (EFS) in IVF / PPT

Empty Follicle Syndrome (EFS) is a rare condition where no oocytes are retrieved despite normal follicular development during an IVF cycle. This can occur even when hormone levels, such as estradiol, suggest that mature eggs should be present. EFS can be related to issues with the trigger shot, the timing of egg retrieval, or intrinsic ovarian factors. It’s important to differentiate between true EFS, where no eggs are ever retrieved, and false EFS, which could result from procedural errors. Understanding EFS helps refine IVF protocols to improve outcomes for patients.

1. Empty Follicle Syndrome (EFS) Dr REHA RAKHOLIA MBBS, MSOBGY , MCH REPRODUCTIVE MEDICINE AND SURGERY Lecture link :https :// www.youtube.com / watch?v =tcdgu3H-pT4&t=272s

2. Empty Follicle Syndrome (EFS) Definition: Empty Follicle Syndrome (EFS) is characterized by the complete failure to retrieve oocytes during IVF, despite normal follicular development ( serial ultrasound) and estradiol levels. Peak estradiol levels in IVF at the time of HCG are usually between 1000 and 4000 pg /ml. . Significance: EFS presents a significant challenge in IVF, leading to unsuccessful retrievals .

3. Physiological Process During follicular development, cumulus cells surround the growing oocyte, linked to mural granulosa cells by junctions. The LH surge, mimicked by HCG or GnRH agonists, breaks these junctions, allowing the cumulus-oocyte complex (COC) to be aspirated (Choi and Smitz , 2014). A successful final trigger is crucial for detaching the COC from the follicle wall.

4. Oocyte Follicle cross talk : Cooperation between oocyte and follicular cells in growing follicle is extremely important. OOCYTE Regulates cumulus cell functions By agents such as GDF9, BMP15 etc CUMULUS CELLS Coordinate oocyte development and maturation, provide energy substrate for oocyte meiosis resumption, regulate oocyte transcription, promote nuclear and cytoplasmic maturation of oocyte.

5. Variants of EFS Genuine EFS ( gEFS ) :it occurs when there is a complete failure to retrieve oocytes despite the correct administration of an ovulation trigger, such as hCG or a GnRH analogue. Rarity : This variant is rare. Trigger Confirmation : Occurs despite optimal hCG levels on the retrieval day or optimal LH levels 12 hours after the agonist trigger. Cycle Outcome : Cannot be rescued with a repeat trigger, making the cycle unsalvageable. False Empty Follicle Syndrome is the failure to retrieve oocytes due to incorrect triggers or technical errors, typically associated with low or inadequate hCG levels from administration issues or improper agonist triggers. Commonality : This variant is more common than genuine EFS. Cycle Outcome : Unlike genuine EFS, false EFS cycles can often be rescued with a repeat trigger, enabling successful oocyte retrieval.

6. Lack of Standardization : No standardized threshold for circulating hCG levels to define a "correct trigger". Wide range of hCG levels (5 to 160 IU/L) reported by different investigators to differentiate GEFS and FEFS. hCG Trigger :Ndukwe et al. (1996): Cut-off value of 10 mIU /L for beta hCG in serum, 36 hours post- hCG administration, predicts EFS with 100% sensitivity and specificity. Incidence Rates : Stevenson et al. (2008): Incidence of GEFS is 33%, and FEFS is 67%.

7. Risk Factors and Mechanisms of Empty Follicle Syndrome (EFS) Risk Factors : Previous history of EFS Advanced age Diminished ovarian reserve Longer duration of infertility Ovarian resistance to various stimulations Obesity Higher baseline FSH levels Lower estradiol levels on the day of trigger Mechanisms : Premature ovulation Low bioavailability of hCG Timing issues from hCG administration to oocyte maturation Unilateral EFS due to ovarian torsion Ovarian aging Defective granulosa cell function Faulty oocyte development

8. Mnemonic for risk factor "POOR EFS" P – Previous history of EFS O – Obesity O – Ovarian resistance to stimulation R – Reduced ovarian reserve (Diminished ovarian reserve) E – Elevated FSH levels (Higher baseline FSH) F – Failed Estradiol response (Lower estradiol levels on the day of trigger) S – Senior age (Advanced age)

9. Incidence Variability in Prevalence: Reported prevalence ranges from 0.045% to 7% of IVF cycles. Impact Cycle cancellation Stress & anxiety for both patients & clinicians Key factors influencing variability: HCG concentration threshold for defining EFS. Choice of patient population (e.g., including or excluding poor responders). Challenges: Uncertain definition leads to inconsistent reporting. Lack of standardization in defining genuine and false EFS.

10. Prognosis after EFS Sporadic event with good clinical outcomes in most of the cases except the 15% that are recurrent cases.( Aktas et al., 2005; Baum et al. 2012) recurrence 20% ( Zreik et al., 2000) Poor outcome in subsequent cycles.( Lorusso et al., 2005; Coskun et al., 2010)

11. Factors Influencing EFS Incidence Patient and Protocol Variables: Patient Population: EFS more common in older patients and those with poor ovarian response ( Aktas et al., 2005). Exclusion of poor responders can underestimate true incidence.

12. Study Sample Size EFS Prevalence Comments/Findings Blazquez et al. (2014) 12,483 considered only egg donor cycles 0.59% 74 EFS cases; 40 fEFS (0.32%) and 21 gEFS (0.16%), 13 unclassified. gEFS defined with positive urinary HCG (10-20 IU/l) or circulating LH < 8 IU/l and progesterone > 3.5 ng/ml at oocyte retrieval( when GnRH-agonist trigger was used) .

13. Aetiology of False Empty Follicle Syndrome (EFS)

14. 1. Insufficient HCG or LH Levels Causes: Incorrect HCG dosage . Errors in self-administration or device setup. Improper injection timing, either too early (<34 hours) or too late (>38 hours), impacting oocyte retrieval.

15. 2 . Industrial Defects in HCG Production Reduced Biological Activity: reduced in-vivo biological activity due to manufacturing defects (e.g., improper storage conditions . ). Storage Conditions: HCG should be stored away from light and below 25°C .

16. 3. Technical Errors During Oocyte Retrieval Issues such as low aspiration pressure or air leakage in the collection system may lead to unsuccessful retrieval

17. fEFS – with hcg trigger called as The pharmaceutical industry syndrome! Errors in administration of the trigger Improper timing of oocyte retrieval Manufacturing defects & potency defects Low bioavailability: may arise from variable absorption or clearance. For women with a history of bariatric surgery, subcutaneous administration of hCG injection can be less effective due to abdominal skin redundancy(intramuscular injections are recommended). Alternatively, rapid liver clearance of hCG (due to desialylation of the hCG molecule) can occur in other patients. Ovarian low bioavailability of hCG

18. fEFS – with GnRH agonist trigger Wrong trigger: Gonadotropin-releasing hormone agonist trigger in a woman with hypogonadotropic hypogonadism (WHO type 1 anovulation) or in an agonist protocol. Inadequate response to agonist trigger: Administering an agonist trigger in a woman with overly suppressed pituitary.

19. Aetiology of Genuine Empty Follicle Syndrome ( gEFS )

20. Aetiology of Genuine Empty Follicle Syndrome ( gEFS ) Genetic factors ZP1 Mutations : Increased Expression of Proapoptotic Genes : LHCGR Gene Mutation Chromosome 2 Inversion : 2. LHCGR Sensitivity and Signal Transduction : 3. Ovarian Aging 4. Poor Ovarian Reserve 5. Faulty Oocyte Development and Maturation 6 . Environmental and Physiological Factors

21. 1. Genetic factors a) ZP1 Mutations : Gene Affected: ZP1 gene, encoding ZP1 glycoproteins. Disrupts secretion of zona pellucida proteins, Preventing formation of zona pellucida. Leads to defective oogenesis and folliculogenesis ; impairs fertilization and implantation. Anti-ZP Autoantibodies: Implicated in inducing Genuine Empty Follicle Syndrome (GEFS).

22. b )Increased Expression of Granulosa Cell Proapoptotic Gene Expression: In patients with recurrent EFS, granulosa cells have shown increased expression of proapoptotic genes and a significant reduction in transcripts essential for normal follicular growth (e.g., PAPP-A, MAPK 3). This imbalance may lead to the loss of oocytes during late folliculogenesis due to apoptosis.

23. c) Receptor Polymorphism LHCGR Mutation : A novel mutation in the LH/ hCG receptor (LHCGR), specifically the p.N400S mutation, has been identified in two sisters with GEFS, inherited as a recessive trait. This mutation causes an irreversible block in the LH signal transmission pathway, rendering repeat administration of hCG ineffective.

24. d) Chromosomal Abnormalities Pericentric Inversion of Chromosome 2 :Vujisic et al. (2005) observed a pericentric inversion in a fragile site of chromosome 2 (46, XX,inv (2)(p11q21)) in a woman with repeated gEFS . Chromosome 2 includes genes coding for Inhibin β b, which are implicated in premature ovarian insufficiency (Shelling et al., 2000).

25. Genetic Predisposition and HCG Response in EFS Partially Impaired Follicular Response to HCG : Ovarian Resistance to HCG: Some patients show resistance to HCG, which can impair follicle maturation. Repeated HCG administration may increase LHCGR stimulation, potentially allowing for oocyte retrieval. Slow Follicular Response to HCG : Extended Time Requirement: Some patients may need more than the typical 36 hours post-HCG to achieve full follicle maturation. Traditional oocyte retrieval scheduling might not be sufficient for these patients.

26. Prolonging interval between ovulation triggering and OPU In Natural Cycle LH surge occurs 34-36 hours prior to ovulation hCG Timing :Exogenous hCG causes follicular rupture after approximately 37 hours. Meiosis begins 18 hours after LH surge LH concentration must be maintained above threshold for 14-27 hours to maximize oocyte maturation Follicle maturation and oocyte maturation is a time dependent process and varies for different women Some women cumulus expansion takes longer and EFS may result when aspiration is done 34hours after hcg

27. 2)LHCGR Sensitivity and Signal Transduction: Potential involvement of LHCGR receptor sensitivity or inefficiency in postreceptor signal transducing pathways. LHCGR activation triggers complex intra-follicular regulations, including the EGF network, which is crucial for oocyte maturation and cumulus expansion .Dysfunction in these pathways has been shown to impair ovulation in animal models, though its role in humans remains unclear.

28. Dual role of FSH in establishing the EGFR signaling axis in the ovarian follicle. FSH induces GCs to express both LHCGR, which enables them to release EGFR ligands in response to the preovulatory LH surge, and EGFR, which enables them to respond to these ligands. The two-step FSH-driven remodeling of the late-follicular environment may ensure an efficient and coordinated response to ovulatory signals.

29. 3. Ovarian Aging Ovarian aging can lead to poor ovarian response, potentially resulting in Empty Follicle Syndrome (EFS). This condition may reflect an advanced stage of ovarian aging where, despite granulosa cells reacting to hormonal signals, the oocytes fail to mature adequately. Thus, viable eggs cannot be retrieved even though follicles look normal on ultrasounds and hormone tests, because the oocytes within aren't developing properly. The prevalence of recurrent EFS increases with age, reaching 57% in women over 40, and is more common with the mini flare-up ovarian stimulation protocol, this protocol mostly used in cases of poor ovarian reserve and aging【Zreik et al., 2000; Madani & Jahangiri , 2015】.

30. 4. Poor Ovarian Reserve Study Overview (Younis, 2012): 439 IVF cycles, 219 women. Women with EFS and poor ovarian responsiveness (below 10th percentile for oocytes) share markers of poor ovarian reserve. Common Markers Identified: Advanced age. Elevated day-3 FSH serum levels. Low peak estradiol levels during stimulation. High-dose gonadotrophins required. Few follicles ≥ 14 mm in diameter on HCG day.

31. Advanced age, high day-3 FSH, low peak estradiol during stimulation, and few well-developed follicles on HCG day are strongly linked to gEFS (Younis et al., 2005). Baum et al. (2012) also found EFS associated with older age, prolonged infertility, and high basal FSH, all indicators of poor ovarian reserve and poor responsiveness to gonadotrophins

32. Alberto Revelli et al experience shows that EFS is about five times more common in women over 40 (6.3%) than in younger women (1.8%), with gEFS being the primary contributor. However, EFS can also occur in younger women with normal or high ovarian reserve. Christopoulos et al. (2015) reported EFS in six younger women (mean age 32.6 years, mean basal FSH 4.4 Ui/l, mean antral follicle count 27) after a GnRH-agonist trigger due to a high risk of ovarian hyperstimulation syndrome. These cases lacked data on LH and progesterone levels at oocyte retrieval, and no distinction was made between false and genuine EFS.

33. 5. Faulty Oocyte Development and Maturation Cumulus Cell Complexes : In GEFS, there is often a strong attachment of cumulus cell complexes to the follicular wall and dysfunctional signaling between the cumulus cells and the oocyte, contributing to faulty oocyte development and maturation.

34. Pathophysiology of Empty Follicle Syndrome (EFS) with Various Triggers

35. 1)Human Chorionic Gonadotropin ( hCG ) Trigger Role: Acts directly on the ovary, serving as a surrogate for LH in the triggering process.hCG mimics the natural LH surge to induce ovulation. Potential Causes of Empty Follicle Syndrome (EFS) with hCG Trigger: Abnormal Folliculogenesis : Issues with the development of the follicles can lead to EFS. Ovarian Response: The ovary may fail to respond adequately to the hCG trigger. Errors in Trigger Administration: Mistakes in the dose, route, or timing of the hCG trigger can result in EFS.

36. 2 . Gonadotropin-releasing Hormone Agonist ( GnRHa ) Trigger Inadequate LH Release: Pituitary may fail to release enough LH to trigger ovulation. Ovarian Receptor Issues: Failure of the ovarian receptors to mediate the action of LH. LH β Subunit Gene Polymorphism: Polymorphisms in this gene can affect LH function.

37. Specific Patient Groups Prone to EFS with Agonist Trigger

38. Hypogonadotropic Hypogonadism (WHO Type 1) : These patients are characterized by very low endogenous levels of FSH and LH (<1.2 IU/L). 2)Borderline Hypothalamic-Pituitary Dysfunction : Patients with gonadotropin levels just above the hypogonadotropic threshold may experience initial follicular development and luteinization, but insufficient LH production prevents complete cumulus cell expansion and detachment from the follicular wall, leading to GEFS or FEFS depending on the pituitary response.

39. 3)Temporary Pituitary Hyposensitivity : In some cycles, a temporary state of hyposensitivity of the pituitary to the agonist trigger may occur. In such cases, an hCG trigger might still recover mature oocytes. 4)Patients with GnRH Receptor Polymorphism : Increased Agonist Dose Requirement 5)Patients with LH Beta Gene Polymorphism: Women with the homozygous variant have a less bioactive LH molecule.This makes them at risk for a blunted response to the agonist trigger.

40. In GnRH agonist trigger Gardner Predicting the probability of not obtaining oocytes after GnRHa  

41. 1 study :Post-trigger LH and progesterone levels strongly correlate with total and mature oocytes retrieved. EFS cases had an LH <15 IU/L and progesterone ≤3.5 ng/mL post-trigger, with an 18.8% probability of EFS at LH <15 IU/L. Another study :An LH ≤15 IU/L post-trigger is associated with lower oocyte yield , yet no impact on oocyte maturity was observed. Monitoring LH levels post-trigger. Gardner

42. Kummer et al.  Chen et al Gardner

43. Predicting successful oocyte retrieval post- GnRHa is critical for deciding on retrieval or rescue hCG dose. Gardner

44. Advantages of GnRHa Trigger Over hCG • Enhanced maturity and quality of oocytes. • Early embryo development benefits. • Hormonal milieu differences at oocyte maturation with GnRHa may contribute to improved outcomes. Gardner

45. Prevention and Early Diagnosis of Empty Follicle Syndrome (EFS)

46. Diagnosis of EFS : KAMINI RAO Hcg trigger Gnrh agonist trigger

47. Post-Trigger Hormone Dynamics and Their Impact on Oocyte Retrieval Luteinization and Progesterone Release : Luteinization of the follicle releases progesterone. Higher number of follicles → Higher progesterone levels. Successful Oocyte Retrieval : Elevated Progesterone + Borderline/Low LH : Can still result in successful oocyte retrieval. Low Progesterone + LH > 15 mU /mL : May indicate inadequate response. KAMINI RAO

48. Timing and Interpretation of Post-Trigger LH and Progesterone Levels Time Interval and Hormone Measurement : Crucial to consider the time interval between the trigger and post-trigger assay, especially for LH. Peak LH Levels : Occur 4 hours post-agonist trigger, followed by a rapid decline. Hormone Level Variations : Shorter Intervals (4-8 hours) : Higher LH and progesterone levels. Longer Intervals (12-15 hours) : Lower LH and higher progesterone levels. KAMINI RAO

49. Risk of EFS Recurrence Medical history of EFS as an Indicator: A history of EFS may suggest an increased risk of recurrence. Some studies view EFS as an irreversible recurrent condition, possibly linked to ovarian aging (Baum et al., 2012; Lorusso et al., 2005; Madani and Jahangiri , 2015). Contrasting View: Other studies argue that a first occurrence of EFS does not necessarily reduce fertility potential in future IVF attempts (Stevenson and Lashen , 2008). Key Point: EFS might not be a persistent condition and does not always predict future IVF outcomes. Revelli A, Carosso A, Grassi G, Gennarelli G, Canosa S, Benedetto C. Empty follicle syndrome revisited: definition, incidence, aetiology, early diagnosis and treatment. Reprod Biomed Online. 2017;35(2):132-138.

50. EFS Outcomes in Subsequent Cycles Clinical Observation: Among 43 patients who repeated IVF after experiencing EFS, 86% obtained mature oocytes in a subsequent cycle, leading to 7 live births. No Significant Difference Found: No significant difference was observed in: Type of protocol used Type of gonadotropin Total exogenous gonadotropin dose Length of ovarian stimulation Peak estradiol level at trigger Type of trigger ( hCG 10,000 IU subcutaneously in all cases) Conclusion: EFS does not invariably recur, and patients can achieve successful outcomes in subsequent cycles. Revelli A, Carosso A, Grassi G, Gennarelli G, Canosa S, Benedetto C. Empty follicle syndrome revisited: definition, incidence, aetiology, early diagnosis and treatment. Reprod Biomed Online. 2017;35(2):132-138.

51. Predicting EFS Before Ovarian Stimulation No Precise Prediction : No exact method to predict EFS before stimulation. Risk Factors : Older age, poor ovarian reserve, and long-duration infertility increase risk but aren't predictive. Limitations: Normal follicular growth and estradiol levels may still result in EFS. Revelli A, Carosso A, Grassi G, Gennarelli G, Canosa S, Benedetto C. Empty follicle syndrome revisited: definition, incidence, aetiology, early diagnosis and treatment. Reprod Biomed Online. 2017;35(2):132-138.

52. Signs and Indicators During Stimulation Positive Indicators: Normal follicular growth. Normal estradiol rise. Warning Signs: Premature ovulation indicators: Precocious Serum progesterone > 1.5 pg /ml. Type II endometrial echogenicity.( mid-secretory phase of the menstrual cycle) Disappearance of bigger size follicle or irregular shape of larger follicles. Revelli A, Carosso A, Grassi G, Gennarelli G, Canosa S, Benedetto C. Empty follicle syndrome revisited: definition, incidence, aetiology, early diagnosis and treatment. Reprod Biomed Online. 2017;35(2):132-138.

53. HCG Administration Guidelines Ensure patients understand the timing and technique for HCG administration. Administer HCG when 2 follicles reach 17–19 mm in diameter with appropriate estradiol levels. Considerations for Polycystic Ovary Patients: Mature oocytes can be retrieved from smaller follicles (14–16 mm). Diagnostic Steps: Conduct urinary or blood HCG test before oocyte retrieval. Puncture follicles one by one and confirm oocyte retrieval before proceeding. Revelli A, Carosso A, Grassi G, Gennarelli G, Canosa S, Benedetto C. Empty follicle syndrome revisited: definition, incidence, aetiology, early diagnosis and treatment. Reprod Biomed Online. 2017;35(2):132-138.

54. Treatment: False EFS

55. Rescue HCG Injection : A second HCG dose hCG from a different batch, higher dose, recombinant hCG and subsequent oocyte retrieval can lead to successful pregnancies, especially when fEFS is diagnosed early. Second Retrieval Success : While some studies report positive outcomes with live births, others have noted lower success rates due to factors like oocyte post-maturity and endometrial receptivity issues. Subsequent Cycle Transfers : In some cases, transferring embryos in a subsequent cycle after rescue HCG treatment may improve implantation and pregnancy rates, potentially due to better endometrial receptivity.

56. Treatment: Genuine EFS

57. Study Protocol Outcomes Take-Home Message Uygur et al. (2003) Prolonging the interval between HCG administration and oocyte retrieval. Results were unsatisfactory; did not improve oocyte retrieval outcomes. Extending the time between HCG administration and oocyte retrieval does not significantly improve outcomes in cases of genuine Empty Follicle Syndrome ( gEFS ). Hassan et al. (1998) no oocytes were retrieved despite HCG circulating levels of 300 IU/l, but after another HCG bolus (10,000 IU) a second OPU 24-h later Retrieved seven mature oocytes after second OPU; two were fertilized via ICSI. Administering a rescue HCG bolus after an initial unsuccessful retrieval can lead to successful oocyte retrieval and fertilization, but it requires careful timing and may not always be effective.

58. Study Protocol Outcomes Lok et al. (2003) Rescue HCG bolus after unsuccessful retrieval despite circulating HCG levels; multiple attempts with different protocols. No oocytes retrieved after repeated cycles; finally achieved oocyte retrieval with GnRH antagonist protocol, but no pregnancy. Suggested endogenous LH stimulus may be effective in some cases. GnRH Antagonist Protocol (Lok et al., 2003): In some patients, switching to a GnRH antagonist protocol can eventually lead to oocyte retrieval after multiple failed attempts. This suggests that an endogenous LH stimulus(by gnRh agonist trigger ) might be more effective than exogenous HCG in certain cases. There is no one-size-fits-all solution for gEFS

59. Study Reference Protocols Outcomes Clinical Implications Beck-Fruchter et al., 2012 Initial cycles with HCG only resulted in no or only immature oocytes retrieved. Subsequent cycle used GnRH agonist (triptorelin acetate) 40h before and HCG 34h before oocyte retrieval. 18 oocytes retrieved (16 mature), 11 embryos developed, 2 transferred, resulting in a singleton pregnancy. Dual triggering with GnRH agonist and HCG may improve outcomes in cases of EFS. Haas et al., 2016 Investigation of mRNA expression changes in granulosa cells after dual triggering with HCG and GnRH-agonist compared to HCG alone. Significant changes in mRNA expression of amphiregulin and epiregulin, suggesting improved oocyte and embryo quality with dual triggering. Supports the efficacy of dual triggering on a molecular level; indicates potential for improving oocyte and embryo quality.

60. Rescue HCG Treatment : Administering a second HCG dose and attempting a second retrieval has been tried with variable success; some cases show improvement while others do not. GnRH-Agonist Trigger with rescue HCG : This method is used more frequently in high responders to reduce the risk of OHSS. It has shown mixed results, with some success but also potential for severe OHSS when combined with rescue HCG. Dual Trigger Approach : Combining HCG and GnRH-agonist (dual triggering) has shown promise in improving oocyte maturation and embryo quality and may be effective for treating recurrent gEFS . Need for Further Research: unknown physiopathology and no well-defined treatment.

61. Step Action Next Steps Retrigger Protocol No oocytes retrieved? - Retrigger with hCG . - Schedule repeat oocyte retrieval for the contralateral ovary 34 hours later. Post-Trigger Serum Level Monitoring (Approx. 12 hours post-trigger) Check LH and Progesterone Intervention Based on Serum Levels No LH/Progesterone Surge? - Retrigger with hCG - Schedule oocyte retrieval 35 hours later. Suboptimal LH Rise (<15 IU/L)? Option A: Retrigger with hCG ASAP & proceed as planned. Option B: Consider canceling the cycle.

62. Physiology: Natural vs GnRHa -induced Mid-cycle Surge GnRHa interacts with GnRH receptors causing a 'flare' of gonadotropins. LH and FSH surge resembles natural mid-cycle surge before ovulation. Natural surge lasts approximately 48 hours with distinct phases. GnRHa -triggered surge is shorter, potentially affecting corpus luteum formation.

63. Comparison: Natural Ovulatory Surge vs. GnRHa -Triggered Surge Natural Ovulatory Surge: Traditionally consists of three phases: abrupt onset (14h), LH peak/plateau (14h), and gradual descent (20h), lasting 48 hours. GnRHa -Triggered Surge: Occurs in two phases: rapid ascent and moderate descent, lasting 24–36 hours. Short duration of LH surge can induce oocyte maturation and ovulation but may result in defective corpus luteum formation.

64. GnRh agonist for triggering final oocyte maturation Gnrha :LH surge and simultaneous FSH surge (Role not fully understood) Advantages of FSH Surge : 1)FSH may induce LH receptor formation in Luteinizing granulosa cells, promote oocyte nuclear maturation and cumulus expansion. ( Byskov et al., 1997 ; Humaidan et al.,2011 ) 2)Gap Junction Maintenance : FSH helps keep gap junctions open between oocytes and cumulus cells, aiding signaling pathways. ( Godard et al., 2009 ; Lamb et al., 2011 ). 3)FSH stimulates Plasminogen activator activity in granulosa cells leading to follicular wall disruption through plasmin and collagenase production. ( Strickland and Beers, 1976 ). 4)Expansion and dispersion of cumulus cells to form an oocyte cumulus mass involves hyaluronic acid matrix stimulated by FSH ( Dell’Aquila et al., 2004 ).

65. Thank you