Fertility Answers - Helping Build Families


Women with lean PCOS share many of the classic symptoms of the syndrome

Polycystic ovary syndrome, PCOS, is one of the most common ovulation disorders in the world. Most women with this disorder share many of its classic symptoms. These include menstrual irregularities, high androgens (male hormones), ovaries presenting with multiple cysts, and weight gain. Women with lean PCOS share many of these same symptoms, except they are typically in a normal weight range.

As it relates to fertility, the hallmark of PCOS is alterations in the ability of the brain to listen to ovarian feedback as eggs grow to be ovulated. This leads to poor egg development, anovulation, and irregular menstruation. Women with PCOS typically do not ovulate, meaning that they will have difficulties getting pregnant without medical intervention.

PCOS has two phenotypes: overweight/obese PCOS and lean PCOS, the latter being much less common. As a subset of PCOS, it is estimated that 20-30% of women with PCOS fall into the lean subcategory. But “lean” doesn’t necessarily mean better. In fact, having this type of PCOS can make it harder to get a diagnosis, even though it causes many of the same long-term health complications as other types of PCOS. If you have lean PCOS, you may face diagnostic delays and long-term health consequences similar to people with overweight/obesity PCOS.

Symptoms and diagnosis

Lean PCOS patients may only display a few symptoms, and irregular periods are a common hallmark. You may have this form of PCOS if you have very infrequent, if not completely absent cycles, a very high resting egg count, a high testosterone level in the blood, and a normal body weight (BMI). Unlike traditional PCOS patients, though, you may not notice some of the other classic symptoms of PCOS like hair growth or acne. Lean PCOS patients are also at risk for things like insulin resistance and prediabetes, but again, not as often as other types of PCOS.

Usually, a lean PCOS diagnosis is based on having high androgen levels in the blood and menstrual cycle issues while at a healthy BMI. Some experts suggest that an ultrasound showing many cysts on the ovaries (polycystic ovaries) should also be considered as part of the diagnosis, but this isn’t always necessary. Testing AMH levels can be useful in the diagnosis of non-obese PCOS as these levels are generally 2–4 times greater in women with the condition. An AMH test indicates a woman’s resting egg count, or egg supply.

Lean PCOS and fertility

Because women with lean PCOS have irregular cycles and ovulate infrequently, getting pregnant can be a challenge. You may not even know you have this condition until you start investigating the reasons you cannot conceive.

Fertility treatment for lean PCOS women is similar to treatment for non-lean PCOS. Ovulation-inducing medicines in conjunction with either intrauterine insemination or in vitro fertilization can help overcome fertility issues. Additionally, adhering to a carefully planned diet and exercise regimen, you may find the severity of your PCOS reduced and your fertility improved. 

In cases where insulin resistance is also involved, medications like metformin may be prescribed to improve metabolic responses to carbohydrates and sugar, ultimately promoting more natural ovulation. However, metformin is less likely to enhance ovulation if insulin resistance is absent. 

For long-term management, women with lean PCOS should aim to maintain a moderate weight. Careful management of your PCOS, even when you’re within a healthy BMI range, can reduce symptoms and side effects. Lifestyle changes, such as increasing nutritional intake, can help manage high blood glucose levels and insulin resistance.