Table of ContentsView AllTable of ContentsWhat Are They?Anatomy & DevelopmentHow Many Follicles?FertilityMenopauseConditionsDiagnosisTreatment
Table of ContentsView All
View All
Table of Contents
What Are They?
Anatomy & Development
How Many Follicles?
Fertility
Menopause
Conditions
Diagnosis
Treatment
Ovarian follicles are small, fluid-filled sacs in theovaries, which are glands located on either side of theuterus. The ovaries contain thousands of follicles, and each month one ruptures to release a mature egg. If you are trying to conceive, your healthcare provider may recommend conducting tests to check your ovarian follicles.
Certain health conditions affect the function of the follicle and may impact fertility. Fortunately, there are treatment options available.
This article explores the anatomy, development, and function of ovarian follicles, as well as the conditions that can affect them.
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What Is an Ovarian Follicle?
An ovarian follicle is a fluid-filled sac in theovary. Each follicle contains one immature egg (oocyte). Duringovulation, one of thousands of follicles ruptures and releases a mature egg. When more than one follicle ruptures and releases an egg, the likelihood of twins increases.
The ovaries have two functions. The first is to release an egg during ovulation. The second is to releaseestrogenandprogesteronethroughout themenstrual cycle.
Most ovarian follicles never release a mature egg. These follicles disintegrate, a process known as atresia. Up to 99% of ovarian follicles disintegrate and never release a mature egg.
A Word From VerywellBecause ovarian follicles are filled with fluid, they are sometimes called ovarian cysts. If your pelvic ultrasound shows multiple small cystic structures on your ovaries, this may be a normal finding.—ANDREA BRADEN, MD, MEDICAL EXPERT BOARD
A Word From Verywell
Because ovarian follicles are filled with fluid, they are sometimes called ovarian cysts. If your pelvic ultrasound shows multiple small cystic structures on your ovaries, this may be a normal finding.—ANDREA BRADEN, MD, MEDICAL EXPERT BOARD
Because ovarian follicles are filled with fluid, they are sometimes called ovarian cysts. If your pelvic ultrasound shows multiple small cystic structures on your ovaries, this may be a normal finding.
—ANDREA BRADEN, MD, MEDICAL EXPERT BOARD
Anatomy and Development of Ovarian Follicles
A person assigned female at birth is born with their total number of ovarian follicles. These follicles develop during gestation and are known as primordial follicles. As the ovarian follicles mature and grow, they become ready to release a mature egg. Most follicles never reach this stage.
Follicular development, known asfolliculogenesis, has several stages:
How Many Follicles Does a Person Have?
The estimated number of follicles at birth varies significantly among studies. Earlier studies stated that people assigned females were born with 2,000,000 primordial follicles.More recent research estimates the number is closer to 100,000 to 600,000 follicles.
Ovarian Follicles and Fertility
When going through fertility treatment, the fertility drugs may cause several ovarian follicles to reach the ovulatory stage each month.
Ovarian Follicles and Menopause
By the time a person reachesmenopause, they will have significantly fewer ovarian follicles than they were born with. Menopause occurs once a person assigned female at birth has no menstrual period for 12 consecutive months and can no longer become pregnant.
Once a person goes through menopause, their ovarian follicles no longer mature and release an egg each month. Several symptoms can occur because the follicles no longer release the same amount of hormones as they used to. Common menopause symptoms includehot flashes,night sweats, andvaginal dryness.
Conditions That May Affect Ovarian Follicles
Several health conditions may affect the ovarian follicles and lead to ovarian function andfertilityissues. Fortunately, there are treatment options available.
Polycystic Ovary Syndrome (PCOS)
PCOSis a chronic syndrome that occurs when a person assigned female at birth experiences hormonal imbalances and problems with metabolism.PCOS causes an excess of immature ovarian follicles and prevents the follicles from maturing.
This leads to a lack of mature eggs and fertility issues. PCOS affects about 6% to 12% of people assigned female at birth who are of reproductive age.
Functional Cysts
When an ovarian follicle does not release a mature egg, it may swell and become a functional cyst.Functional ovarian cystsare not cancerous and may cause pelvic pain. People with PCOS or endometriosis (when tissue similar to that in the uterus grows outside the uterus) are at an increased risk of functional ovarian cysts.
Your healthcare provider can diagnose functional cysts with a pelvic ultrasound. Some may resolve on their own, while others may require treatment.
Primary Ovarian Insufficiency
Primary ovarian insufficiencyoccurs when a person’s ovaries fail and stop functioning before age 40. People with primary ovarian insufficiency often experience irregular periods, a low number of ovarian follicles, and fertility issues.
People who have primary ovarian insufficiency have ovarian follicles that do not release a mature egg every month.
Ruptured Ovarian Cysts
Ovarian cysts are common, and most are harmless. An ovarian cyst can break or rupture. When a cyst ruptures, you may experience vaginal spotting,abdominal bloating, and sudden back pain.
How Conditions That Affect Ovarian Follicles Are Diagnosed
If you are experiencinginfertility issues, your healthcare provider may recommend checking your ovarian follicles to determine the underlying cause. Diagnostic tests for conditions that affect ovarian follicles include:
How Conditions That Affect Ovarian Follicles Are Treated
Fortunately, many of the conditions that affect ovarian follicles can be treated. Possible treatment options include:
Summary
Ovarian follicles are tiny, fluid-filled sacs in the ovaries. Ovarian follicles contain immature eggs. An ovarian follicle matures and ruptures each month to release a mature egg. In addition to releasing mature eggs, ovarian follicles secrete estrogen and progesterone hormones.
Certain health conditions affect the function of ovarian follicles. These include ovarian cysts, primary ovarian insufficiency, and PCOS. These conditions are often diagnosed with a medical history, physical exam, pelvic exam, blood tests, and pelvic ultrasound. Fortunately, there are several treatment options available.
19 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.National Cancer Institute.Definition of ovarian follicle.American Society for Reproductive Medicine.Multiple pregnancy and birth: Twins, triplets, and high-order multiples.Zhang J, Liu Y, Yao W, Li Q, Liu H, Pan Z.Initiation of follicular atresia: gene networks during early atresia in pig ovaries.Reproduction. 2018;156(1):23-33. doi:10.1530/REP-18-0058Li L, Shi X, Shi Y, Wang Z.The signaling pathways involved in ovarian follicle development.Front Physiol. 2021;12:730196. doi:10.3389/fphys.2021.730196Zhou J, Peng X, Mei S.Autophagy in ovarian follicular development and atresia.Int J Biol Sci. 2019;15(4):726-737. doi:10.7150/ijbs.30369Scheffer GJ, Broekmans FJ, Looman CW, et al.The number of antral follicles in normal women with proven fertility is the best reflection of reproductive age.Hum Reprod. 2003;18(4):700-706. doi:10.1093/humrep/deg135Lawley SD, Johnson J.Why is there an “oversupply” of human ovarian follicles?†.Biol Reprod. 2023;108(5):814-821. doi:10.1093/biolre/ioad022Chin HB, Baird DD, Kaplan SL, et al.Characterization of ovarian development in girls from birth to 9 months.Paediatr Perinat Epidemiol. 2021;35(1):75-82. doi:10.1111/ppe.12673Geber S, Megale R, Vale F, Lanna AM, Cabral AC.Variation in ovarian follicle density during human fetal development.J Assist Reprod Genet. 2012;29(9):969-972. doi:10.1007/s10815-012-9810-2Casalechi M, Di Stefano G, Fornelli G, Somigliana E, Viganò P.Impact of endometriosis on the ovarian follicles.Best Pract Res Clin Obstet Gynaecol. 2024;92:102430. doi:10.1016/j.bpobgyn.2023.102430Office on Women’s Health.Menopause basics.Depmann M, Faddy MJ, van der Schouw YT, et al.The relationship between variation in size of the primordial follicle pool and age at natural menopause.J Clin Endocrinol Metab. 2015;100(6):E845-E851. doi:10.1210/jc.2015-1298Centers for Disease Control and Prevention.Diabetes and polycystic ovary syndrome (PCOS).Office on Women’s Health.Polycystic ovary syndrome.MedlinePlus.Polycystic ovary syndrome.American College of Obstetricians and Gynecologists.Ovarian cysts.National Institute of Child Health and Human Development.Primary ovarian insufficiency.Ford EA, Beckett EL, Roman SD, McLaughlin EA, Sutherland JM.Advances in human primordial follicle activation and premature ovarian insufficiency.Reproduction. 2020;159(1):R15-R29. doi:10.1530/REP-19-0201MedlinePlus.Primary ovarian insufficiency.
19 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.National Cancer Institute.Definition of ovarian follicle.American Society for Reproductive Medicine.Multiple pregnancy and birth: Twins, triplets, and high-order multiples.Zhang J, Liu Y, Yao W, Li Q, Liu H, Pan Z.Initiation of follicular atresia: gene networks during early atresia in pig ovaries.Reproduction. 2018;156(1):23-33. doi:10.1530/REP-18-0058Li L, Shi X, Shi Y, Wang Z.The signaling pathways involved in ovarian follicle development.Front Physiol. 2021;12:730196. doi:10.3389/fphys.2021.730196Zhou J, Peng X, Mei S.Autophagy in ovarian follicular development and atresia.Int J Biol Sci. 2019;15(4):726-737. doi:10.7150/ijbs.30369Scheffer GJ, Broekmans FJ, Looman CW, et al.The number of antral follicles in normal women with proven fertility is the best reflection of reproductive age.Hum Reprod. 2003;18(4):700-706. doi:10.1093/humrep/deg135Lawley SD, Johnson J.Why is there an “oversupply” of human ovarian follicles?†.Biol Reprod. 2023;108(5):814-821. doi:10.1093/biolre/ioad022Chin HB, Baird DD, Kaplan SL, et al.Characterization of ovarian development in girls from birth to 9 months.Paediatr Perinat Epidemiol. 2021;35(1):75-82. doi:10.1111/ppe.12673Geber S, Megale R, Vale F, Lanna AM, Cabral AC.Variation in ovarian follicle density during human fetal development.J Assist Reprod Genet. 2012;29(9):969-972. doi:10.1007/s10815-012-9810-2Casalechi M, Di Stefano G, Fornelli G, Somigliana E, Viganò P.Impact of endometriosis on the ovarian follicles.Best Pract Res Clin Obstet Gynaecol. 2024;92:102430. doi:10.1016/j.bpobgyn.2023.102430Office on Women’s Health.Menopause basics.Depmann M, Faddy MJ, van der Schouw YT, et al.The relationship between variation in size of the primordial follicle pool and age at natural menopause.J Clin Endocrinol Metab. 2015;100(6):E845-E851. doi:10.1210/jc.2015-1298Centers for Disease Control and Prevention.Diabetes and polycystic ovary syndrome (PCOS).Office on Women’s Health.Polycystic ovary syndrome.MedlinePlus.Polycystic ovary syndrome.American College of Obstetricians and Gynecologists.Ovarian cysts.National Institute of Child Health and Human Development.Primary ovarian insufficiency.Ford EA, Beckett EL, Roman SD, McLaughlin EA, Sutherland JM.Advances in human primordial follicle activation and premature ovarian insufficiency.Reproduction. 2020;159(1):R15-R29. doi:10.1530/REP-19-0201MedlinePlus.Primary ovarian insufficiency.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
National Cancer Institute.Definition of ovarian follicle.American Society for Reproductive Medicine.Multiple pregnancy and birth: Twins, triplets, and high-order multiples.Zhang J, Liu Y, Yao W, Li Q, Liu H, Pan Z.Initiation of follicular atresia: gene networks during early atresia in pig ovaries.Reproduction. 2018;156(1):23-33. doi:10.1530/REP-18-0058Li L, Shi X, Shi Y, Wang Z.The signaling pathways involved in ovarian follicle development.Front Physiol. 2021;12:730196. doi:10.3389/fphys.2021.730196Zhou J, Peng X, Mei S.Autophagy in ovarian follicular development and atresia.Int J Biol Sci. 2019;15(4):726-737. doi:10.7150/ijbs.30369Scheffer GJ, Broekmans FJ, Looman CW, et al.The number of antral follicles in normal women with proven fertility is the best reflection of reproductive age.Hum Reprod. 2003;18(4):700-706. doi:10.1093/humrep/deg135Lawley SD, Johnson J.Why is there an “oversupply” of human ovarian follicles?†.Biol Reprod. 2023;108(5):814-821. doi:10.1093/biolre/ioad022Chin HB, Baird DD, Kaplan SL, et al.Characterization of ovarian development in girls from birth to 9 months.Paediatr Perinat Epidemiol. 2021;35(1):75-82. doi:10.1111/ppe.12673Geber S, Megale R, Vale F, Lanna AM, Cabral AC.Variation in ovarian follicle density during human fetal development.J Assist Reprod Genet. 2012;29(9):969-972. doi:10.1007/s10815-012-9810-2Casalechi M, Di Stefano G, Fornelli G, Somigliana E, Viganò P.Impact of endometriosis on the ovarian follicles.Best Pract Res Clin Obstet Gynaecol. 2024;92:102430. doi:10.1016/j.bpobgyn.2023.102430Office on Women’s Health.Menopause basics.Depmann M, Faddy MJ, van der Schouw YT, et al.The relationship between variation in size of the primordial follicle pool and age at natural menopause.J Clin Endocrinol Metab. 2015;100(6):E845-E851. doi:10.1210/jc.2015-1298Centers for Disease Control and Prevention.Diabetes and polycystic ovary syndrome (PCOS).Office on Women’s Health.Polycystic ovary syndrome.MedlinePlus.Polycystic ovary syndrome.American College of Obstetricians and Gynecologists.Ovarian cysts.National Institute of Child Health and Human Development.Primary ovarian insufficiency.Ford EA, Beckett EL, Roman SD, McLaughlin EA, Sutherland JM.Advances in human primordial follicle activation and premature ovarian insufficiency.Reproduction. 2020;159(1):R15-R29. doi:10.1530/REP-19-0201MedlinePlus.Primary ovarian insufficiency.
National Cancer Institute.Definition of ovarian follicle.
American Society for Reproductive Medicine.Multiple pregnancy and birth: Twins, triplets, and high-order multiples.
Zhang J, Liu Y, Yao W, Li Q, Liu H, Pan Z.Initiation of follicular atresia: gene networks during early atresia in pig ovaries.Reproduction. 2018;156(1):23-33. doi:10.1530/REP-18-0058
Li L, Shi X, Shi Y, Wang Z.The signaling pathways involved in ovarian follicle development.Front Physiol. 2021;12:730196. doi:10.3389/fphys.2021.730196
Zhou J, Peng X, Mei S.Autophagy in ovarian follicular development and atresia.Int J Biol Sci. 2019;15(4):726-737. doi:10.7150/ijbs.30369
Scheffer GJ, Broekmans FJ, Looman CW, et al.The number of antral follicles in normal women with proven fertility is the best reflection of reproductive age.Hum Reprod. 2003;18(4):700-706. doi:10.1093/humrep/deg135
Lawley SD, Johnson J.Why is there an “oversupply” of human ovarian follicles?†.Biol Reprod. 2023;108(5):814-821. doi:10.1093/biolre/ioad022
Chin HB, Baird DD, Kaplan SL, et al.Characterization of ovarian development in girls from birth to 9 months.Paediatr Perinat Epidemiol. 2021;35(1):75-82. doi:10.1111/ppe.12673
Geber S, Megale R, Vale F, Lanna AM, Cabral AC.Variation in ovarian follicle density during human fetal development.J Assist Reprod Genet. 2012;29(9):969-972. doi:10.1007/s10815-012-9810-2
Casalechi M, Di Stefano G, Fornelli G, Somigliana E, Viganò P.Impact of endometriosis on the ovarian follicles.Best Pract Res Clin Obstet Gynaecol. 2024;92:102430. doi:10.1016/j.bpobgyn.2023.102430
Office on Women’s Health.Menopause basics.
Depmann M, Faddy MJ, van der Schouw YT, et al.The relationship between variation in size of the primordial follicle pool and age at natural menopause.J Clin Endocrinol Metab. 2015;100(6):E845-E851. doi:10.1210/jc.2015-1298
Centers for Disease Control and Prevention.Diabetes and polycystic ovary syndrome (PCOS).
Office on Women’s Health.Polycystic ovary syndrome.
MedlinePlus.Polycystic ovary syndrome.
American College of Obstetricians and Gynecologists.Ovarian cysts.
National Institute of Child Health and Human Development.Primary ovarian insufficiency.
Ford EA, Beckett EL, Roman SD, McLaughlin EA, Sutherland JM.Advances in human primordial follicle activation and premature ovarian insufficiency.Reproduction. 2020;159(1):R15-R29. doi:10.1530/REP-19-0201
MedlinePlus.Primary ovarian insufficiency.
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