Polyendocrine Metabolic Ovarian Syndrome (PMOS, formerly known as PCOS) 

Understanding PMOS

Polyendocrine Metabolic Ovarian Syndrome (PMOS) is a complex hormonal and metabolic disorder that affects the ovaries, endocrine system, and the body’s metabolism. Clinically, PMOS is commonly characterized by irregular or absent menstrual periods, acne, and excess facial or body hair growth. Physiologically, the condition is associated with irregular ovulation, elevated androgen levels, insulin resistance, and metabolic dysfunction. PMOS is one of the most common causes of infertility and menstrual irregularities in reproductive-age women.

PMOS is considered a polyendocrine disorder because it involves multiple hormone-producing systems in the body, including the ovaries, pancreas, adrenal glands, and fat tissue. It is also considered a metabolic disorder because it is strongly associated with insulin resistance, weight gain, inflammation, and an increased risk of diabetes and cardiovascular disease.

Recent Change in Terminology: PCOS to PMOS

Historically, this condition has been known as Polycystic Ovary Syndrome (PCOS). However, many experts and advocacy groups have begun using the term Polyendocrine Metabolic Ovarian Syndrome (PMOS) to better reflect the true nature of the disorder.

The older name, PCOS, placed focus on ovarian cysts, even though many affected women do not actually have ovarian cysts. The newer term emphasizes that the condition involves:

• Multiple endocrine (hormonal) systems
• Significant metabolic dysfunction
• Ovarian and reproductive health concerns

The updated terminology helps provide a more accurate understanding of the condition and encourages a broader approach to diagnosis and treatment.

What Happens During Normal Ovulation?

Each month, the ovaries begin to develop several small follicles, tiny collections of fluid that each contain an egg. Early in the menstrual cycle, one follicle is “recruited.” This “dominant follicle” grows larger than the rest and ultimately releases an egg at the time of ovulation.

After ovulation, the follicle becomes a structure called the corpus luteum. If fertilization occurs, the corpus luteum continues producing hormones to support early pregnancy. If fertilization does not occur, the corpus luteum resolves, and menstruation occurs approximately two weeks later.

How Does PMOS Affect Ovulation?

In women with PMOS, many follicles begin to develop inside the ovaries, but an egg is not released regularly. Women with PMOS are usually either:

• Anovulatory: they do not ovulate at all
• Oligo-ovulatory: they ovulate infrequently or unpredictably

Because ovulation occurs irregularly or not at all, menstrual cycles become disrupted and fertility may be affected.

What Are the Symptoms of PMOS?

Since ovulation is necessary for pregnancy, women with PMOS frequently experience difficulty conceiving. Because ovulation also triggers the hormonal changes that lead to menstruation, many women with PMOS have irregular or absent periods.

Additional symptoms include (but are not limited to): 

• Weight gain or difficulty losing weight
• Insulin resistance
• Fatigue
• Acne or oily skin
• Excess facial or body hair growth (hirsutism)
• Thinning scalp hair or male-pattern hair loss
• Darkening of the skin, especially around the neck or underarms
• Mood changes, anxiety, or depression

Symptoms can vary significantly from person to person.

Do the Ovaries Look Different with PMOS?

The ovaries in women with PMOS oftentimes have a characteristic appearance on ultrasound (sonography), although this is not always the case.

During a “normal” menstrual cycle, several follicles begin developing within the ovaries each month. Hormonal fluctuations throughout the cycle allow one follicle to mature more than the others. This dominant follicle eventually ruptures and releases an egg, a process known as ovulation. Once ovulation occurs, the egg has an opportunity to be fertilized and pregnancy can occur. If pregnancy does not occur, a series of hormonal changes leads to a menstrual period approximately two weeks later.

In individuals with PMOS, hormonal signaling does not follow the typical pattern. Because ovulation is disrupted or inconsistent, many follicles begin developing but never fully mature or release an egg. Instead, these immature follicles remain within the ovaries and accumulate over time. This collection of arrested follicles often creates the classic “polycystic” or “string of pearls” appearance often seen on ultrasound, and the ovaries may become enlarged due to the buildup of these undeveloped follicles. 

The arrested follicles are sometimes referred to as “cysts.” Importantly, they are not dangerous ovarian cysts or tumors, but rather immature follicles that have stalled in development because of the hormonal and metabolic disruptions associated with PMOS.

However, not all women with PMOS have polycystic-appearing ovaries, which is one reason the newer terminology more accurately reflects the condition. In fact, many women with PMOS ovulate regularly, especially when their condition is well-managed through dietary, lifestyle, and metabolic interventions.

What Happens When Hormones Are Dysregulated?

PMOS represents a complex hormonal imbalance involving several endocrine systems. The ovaries may produce:

• Higher-than-normal androgen levels (male-type hormones), which may cause:
  • Increased facial or body hair growth
  • Acne
  • Thinning scalp hair
• Too much estrogen and not enough progesterone, contributing to:
  • Irregular menstrual cycles
  • Fertility challenges
  • Thickening of the uterine lining

In many women, insulin resistance also plays a major role. Elevated insulin levels can stimulate the ovaries to produce more androgens, worsening symptoms, and disrupting ovulation further.

Why Is PMOS Considered a Metabolic Disorder?

PMOS affects not only reproductive hormones but also the body’s metabolism. Many women with PMOS have:

• Insulin resistance (when the body’s cells don’t respond normally to insulin) 
• Elevated insulin levels
• Increased abdominal weight gain
• Abnormal cholesterol levels
• Chronic low-grade inflammation

Because of these metabolic changes, women with PMOS may have an increased risk of:

• Type 2 diabetes
• Prediabetes
• High blood pressure
• Heart disease
• Sleep apnea
• Fatty liver disease

This is why long-term medical monitoring is important, even beyond fertility concerns.

What Are the Risks of Having PMOS?

Women with PMOS have an increased risk of endometrial hyperplasia and endometrial cancer. Normally, the uterine lining builds up each month and sheds during menstruation. When ovulation does not occur regularly, the lining may continue to build without regular shedding, increasing the risk of abnormal overgrowth.

Additional long-term health risks may include:

• Infertility
• Type 2 diabetes
• Cardiovascular disease
• Obesity-related complications
• Anxiety and depression

What Causes PMOS?

The exact cause of PMOS is not fully understood, but several contributing factors have been identified:

Genetics

PMOS often runs in families. Sisters or mothers may share symptoms such as irregular periods, infertility, or metabolic problems.

Insulin Resistance

Many women with PMOS have insulin resistance, meaning the body does not respond effectively to insulin. Elevated insulin levels can disrupt hormone production and ovulation.

Weight and Metabolism

Excess body fat can worsen hormonal imbalance because fat tissue is hormonally active and contributes to inflammation and insulin resistance.

Inflammation

Chronic low-grade inflammation may also contribute to increased androgen production and metabolic dysfunction.

Is PMOS a Lifelong Condition?

While there is currently no known cure for PMOS, many treatments can help manage symptoms and reduce long-term health risks.

Treatment Options May Include:

Lifestyle Changes

Weight loss, regular exercise, balanced nutrition, and improved sleep can significantly improve hormone balance and insulin sensitivity. Even a 5–10% reduction in body weight may restore ovulation in some women.

Birth Control Pills

Combined hormonal contraceptives containing estrogen and progestin are commonly used to regulate menstrual cycles and reduce androgen-related symptoms.

Medications to Improve Insulin Resistance

Medications such as metformin, commonly used to treat diabetes, may help improve insulin sensitivity and support more regular ovulation. Certain supplements are oftentimes recommended to help with insulin resistance as well. 

Fertility Treatments

Women trying to conceive may be treated with medications that stimulate ovulation.

Management of Metabolic Health

Diet and exercise are cornerstones of PMOS management, as they help improve insulin sensitivity and reduce the risk of metabolic disease. Long-term monitoring of blood sugar, cholesterol, blood pressure, and cardiovascular health is also important in individuals with PMOS.

Living with PMOS

PMOS is a lifelong endocrine and metabolic condition, but with appropriate treatment and lifestyle management, many women successfully manage symptoms, protect their long-term health, and achieve pregnancy if desired. Early diagnosis and comprehensive care are important to improving quality of life and reducing future health risks.