Definition - What does Lean PCOS mean?

Lean polycystic ovarian syndrome (PCOS) occurs when women have a diagnosis of PCOS, but are not overweight. It is common for women diagnosed with PCOS to be overweight however, this is not always the case. Around 20% of women with PCOS have lean PCOS and may be of average weight or underweight and still experience symptoms of PCOS and may experience problems with fertility. Lean is generally defined as having a body mass index (BMI) of less than 25.

Women with PCOS have abnormalities in the production of hormones. Higher than normal levels of male hormones called androgens are produced causing the classic symptoms of PCOS that may include menstrual cycle irregularities, inhibition of ovulation (anovulation), and problems regulating blood sugar.

FertilitySmarts explains Lean PCOS

Despite being of average weight, women with lean PCOS may experience issues with fertility similar to women with classic PCOS features. Although body mass index (BMI) may be normal, insulin resistance and higher than normal circulating insulin is common and can cause excess production of androgens. Because androgens generally act to produce male characteristics, the menstrual cycle may become irregular and ovulation may not occur regularly. Metabolic side effects like diabetes and insulin resistance are found in lower levels in woman with lean PCOS than those with PCOS who are overweight.

Secondary symptoms like acne and facial hair (hirsutism) are also common. Women with lean PCOS may have many follicles present in the ovaries but without the appropriate hormonal signals, do not progress to mature eggs. Regulating insulin production and the body's response to insulin is an important factor in improving fertility in women with lean PCOS and can be achieved with diet and physical activity as well as medication and surgical options are also available.

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