The Female Reproductive System and Polycystic Ovarian Syndrome
by Robert Tallitsch, PhD | August 22, 2023
Video explaining the female reproductive system and polycystic ovarian syndrome using a real patient case study!
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(A note on sex and gender: Sex and gender exist on a spectrum. This Brain Builder article will use the terms “female” and “male,” or both, to refer to the sex assigned to the individual at birth.)
The latest statistics from the National Institutes of Health (NIH) indicate that, in 2020, the number of females in child-bearing age affected with polycystic ovarian syndrome (PCOS) ranged from one out of ten to one out of seven. This Brain Builder will discuss the anatomy of the ovaries, and the symptoms, possible causes, and treatment options for polycystic ovarian syndrome (also termed PCOS).
Anatomy of the Ovaries
The ovaries are small, paired organs located within the female pelvic cavity. Functionally, the ovaries produce female gametes (oocytes) and secrete hormones.
Most females are born with two ovaries. Even though it is quite rare, some females (approximately one out of 11,000) are born with only one ovary. It is even more rare (one out of 29,000) for a female to have a supernumerary (third) ovary.
Each ovary is oval in shape and approximately 4 cm by 2 cm in size. Although the position of the ovaries within the pelvic cavity is quite variable (especially during pregnancy), each ovary is located within an ovarian fossa. The ovarian fossae are depressions of the posterolateral aspects of the pelvic cavity, with one being located on each side of the pelvic cavity. The ovaries are bordered by the iliac arteries, with the external iliac artery being superior to the ovary, and the internal iliac being inferior to the ovary.
The ovaries are held in shape by a combination of connective tissue pieces termed ligaments. The mesovarium attaches the ovary to the posterior aspect of the broad ligament. The portion of the broad ligament that is located between the mesovarium and the lateral wall of the pelvic wall is termed the suspensory ligament (also termed the suspensory ligament of the ovary). In addition, the ovary is connected to the lateral wall of the uterus by the round ligament (round ligament of the ovary).
Histology of the Ovary
The surface of the ovary is surrounded by a modified portion of the peritoneum termed the surface epithelium (also termed the germinal epithelium).
When viewed in cross section the ovary is composed of two zones: an inner medulla and an outer cortex. The medulla is composed of a loose framework of connective tissue, lymphatics, blood vessels, and nerves.
The cortex is composed of compact, richly cellular connective tissue containing the ovarian follicles in various stages of development and degeneration. The size and histological appearance of each follicle is dependent on the stage of development. Each follicle is composed of an oocyte surrounded by epithelial cells. Larger follicles also contain one or two layers of connective tissue. The follicles of the ovary are divided into following stages of development:
- Primordial follicles are the most abundant and smallest of the follicles. These follicles are located at the periphery of the cortex.
- Primary follicles, under the effect of the female hormones, have started to enlarge in size. Primary follicles have moved slightly deeper within the cortex of the ovary.
- Secondary follicles (also termed antral or growing follicles) continue to mature and move deeper within the cortex. In this developmental stage a fluid-filled cavity, termed the antrum, has started to develop within the layers of the follicle.
- Mature (also termed Graafian, ovulatory, or tertiary) follicles are the largest of the developmental stages, spanning the entire width of the cortex and causing a bulge on the surface of the follicle. This is the stage of follicular development that prepares for and may ultimately undergo ovulation.
Further histological examination of an ovary demonstrates numerous follicles undergoing a form of degeneration termed follicular atresia. Atresia may begin during any phase of follicular development.
Current thinking is that a female is born with all of the oocytes she will ever possess. In addition, a female typically ovulates via alternating ovaries (right ovary during one cycle, left ovary during the next). Finally, only one follicle will typically undergo ovulation at a time, with the remaining mature follicles undergoing atresia.
Polycystic Ovarian Syndrome
Polycystic Ovarian Syndrome (PCOS) is one of the most common causes of female infertility. Females with PCOS have a hormonal imbalance and metabolic problems that have the potential to affect the individual’s overall, long-term health.
Symptoms of polycystic ovarian syndrome either start around the time of the first menstrual period or later in life. The symptoms for PCOS vary considerably. A positive diagnosis for PCOS is typically made when the female exhibits abnormal menstrual periods that are irregular in duration and frequency, possesses ovaries that are abnormally large and/or have numerous cysts, and exhibits higher-than-normal blood levels of androgen. Additional symptoms often include:
- Weight gain
- Infertility
- Hirsutism, which is defined as excessive body hair, including on the back, chest, and/or stomach.
- Acne or oily skin
- Thinning hair on the head in the form of pattern baldness
- Dark or thick skin patches under the breasts, on the back of the neck, or in the armpits
PCOS often develops when a female is unable to ovulate. This results in the development of many small cysts within the ovary. These cysts then produce androgenic hormones, which can cause additional problems with the menstrual cycle. In addition, these androgenic hormones may cause many of the other symptoms of PCOS.
The exact underling cause of polycystic ovarian syndrome is unknown. Current research points to several possible causes of PCOS:
- Genetic predisposition for PCOS
- High insulin levels
- High levels of androgenic hormones that inhibit ovulation by the female
- Low-grade inflammation within the ovaries, resulting in polycystic ovaries producing higher-than-normal levels of androgens
PCOS treatment is determined by a variety of factors, including the patient’s age, severity of symptoms, and overall health prior to the onset of PCOS. In addition, treatment options will also be determined depending on whether or not the patient wishes to get pregnant in the future.
If the patient does not wish to become pregnant treatment options include:
- Birth control pills
- Diabetes medication to lower insulin resistance in the patient. Diabetes medication may also help to reduce the production of androgens by the ovaries, which will help slow hair growth and may help to increase the chances of regular menstrual cycles.
- Changes in diet and activity, in order to reduce the patient’s weight and reduce other symptoms of PCOS
Treatment for a patient that wishes to become pregnant in the future often includes one or more of the following options:
- Medications to enhance ovulation.
- Changes in diet and activity level, which may:
- help the body to use insulin more efficiently.
- lower blood glucose levels
- increase the ovary’s ability to ovulate.
- reduce the severity of PCOS symptoms.
If left untreated, polycystic ovarian syndrome may produce one or more of the following complications:
- Infertility
- Type 2 diabetes or prediabetic symptoms
- Miscarriage or premature births
- Metabolic syndrome, which is a series of symptoms including high levels of LDL (low-density lipoproteins), high blood pressure, and high blood sugar.
- Sleep apnea
- Endometrial cancer
- Depression, anxiety, and eating disorders.
- Nonalcoholic steatohepatitis, which is a severe liver inflammation caused by high levels of fat development within the liver.
Polycystic ovarian syndrome can be treated successfully. Depending on the patient’s age proper treatment often results in a patient of child-bearing age having normal menstrual periods and having an increased chance of becoming pregnant. In older individuals' proper treatment of PCOS will help reduce excessive hear growth, weight gain, and the chances of becoming diabetic.
Key Terms
PCOS - An abbreviation for polycystic ovarian syndrome, which is one of the most common forms of female infertility.
Ovary - The ovaries are small, paired organs located within the female pelvic cavity. Functionally, the ovaries produce female gametes (oocytes) and secrete hormones.
Hirsutism - Excessive body hair, including on the back, chest, and/or stomach of a female.
Ovarian fossa - Each ovary is located within an ovarian fossa. The ovarian fossae are depressions of the posterolateral aspects of the pelvic cavity, with one being located on each side of the pelvic cavity.
Mature follicle - Mature follicles are also termed Graafian ovulatory, or tertiary, follicles. These follicles are the largest of the developmental stages, spanning the entire width of the cortex and causing a bulge on the surface of the follicle. This is the stage of follicular development that prepares for and may ultimately undergo ovulation.
Primordial follicle - Primordial follicles are the most abundant and smallest of the follicles. These follicles are located at the periphery of the cortex.
Germinal epithelium - The surface of the ovary is surrounded by a modified portion of the peritoneum termed the surface epithelium, also termed the geminal epithelium.
Secondary follicle - Secondary follicles (also termed antral or growing follicles) continue to mature and move deeper within the cortex. In this developmental stage a fluid-filled cavity, termed the antrum, has started to develop within the layers of the follicle.
Tunica albuginea - The tunica albuginea is a thin fibrous capsule found deep to the surface epithelium of the ovary.
Metabolic syndrome - A series of symptoms including high levels of LDL (low-density lipoproteins), high blood pressure, and high blood sugar.
Nonalcoholic steatohepatitis - A severe inflammation of the liver, caused by high levels of fat development within the liver.
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