Both congenital adrenal hyperplasia (CAH) and polycystic ovary syndrome (PCOS) involve high levels of androgens, and these conditions look similar. Late-onset CAH may be mistaken for PCOS. Because their symptoms can overlap, lab testing is needed to help your doctor tell them apart and recommend the most effective treatment.

How Common Are Congenital Adrenal Hyperplasia and Polycystic Ovary Syndrome?

Also known as polycystic ovarian syndrome, PCOS is the most common endocrine (hormonal) condition in women during their reproductive years — it affects up to 10 percent of women, according to the Journal of the Endocrine Society. CAH is much less common.

Classic CAH is usually diagnosed at birth. Nonclassic CAH (NC-CAH), also called late-onset CAH, often shows up later — in childhood, the teen years, or adulthood — and can resemble PCOS.

Nonclassic CAH affects about 1 in 1,000 people. It’s diagnosed more often in women because symptoms like irregular periods or facial hair are more likely to be noticed. PCOS is about 40 to 50 times more common than NC-CAH among women of reproductive age, according to the journal Frontiers in Endocrinology.

Similarities of Congenital Adrenal Hyperplasia and Polycystic Ovary Syndrome

Congenital adrenal hyperplasia can look the same as PCOS. Here are four key features they share.

1. Both PCOS and CAH Can Cause High Levels of Androgen Hormones

In women, both PCOS and CAH can lead to hyperandrogenism — high levels of androgens like testosterone, sometimes called male sex hormones. Normally, the ovaries and adrenal glands produce these hormones in small amounts. But when too much is made, androgen excess can affect body hair, skin, and the menstrual cycle.

PCOS is a much more common cause of high androgen levels. Nonclassic CAH is less common, accounting for just 1 percent to 4 percent of cases of androgen excess, and is often mistaken for PCOS.

2. Problems With Infertility May Occur in Both

PCOS is one of the most common causes of infertility in females, according to Cleveland Clinic. High androgen levels can interfere with ovulation (the monthly release of an egg from the ovaries), making it irregular or even stopping it.

Up to 75 percent of people with PCOS experience infertility, either directly or as a side effect of other symptoms. Similarly, up to 13 percent of women with nonclassic CAH experience infertility, according to Frontiers in Endocrinology. Although infertility is less common in CAH than in PCOS, the causes and treatments are similar.

Both CAH and PCOS can cause symptoms such as excess hair growth, hair loss, and problems with fertility.

3. Both Conditions Can Cause Excess Hair Growth or Hair Loss

Androgens affect hair follicles and can change hair growth patterns in both CAH and PCOS.

Excess Hair Growth

“Hirsutism” is the medical term for extra dark, coarse body hair growth in areas such as these:

• Chin and jaw
• Chest
• Lower abdomen
• Back
• Inner thighs
• Arms

Up to 70 percent of people with PCOS experience hirsutism. This is also a common — but usually milder NC-CAH symptom.

Hair Loss

High androgen levels can also lead to androgenic alopecia — hair loss on the scalp. This type can start as a bald spot, a receding hairline, or thinning hair all over the head.

4. Both Raise the Risk of Metabolic Syndrome

Hormonal imbalances caused by CAH and PCOS can affect metabolism — the way the body uses food for energy. This can raise the risk of metabolic syndrome, a cluster of conditions including:

• Excess belly fat
• Insulin resistance, which may lead to type 2 diabetes
• High cholesterol or triglycerides
• Increased risk of cardiovascular diseases

Key Differences Between Congenital Adrenal Hyperplasia and Polycystic Ovary Syndrome

Although CAH and PCOS can look similar, especially in symptoms and certain blood test results, some important differences help tell them apart.

1. Genetic Testing Can Diagnose CAH but Not PCOS

Classic CAH, which is typically diagnosed at birth, can be identified in prenatal testing if a sibling has already been diagnosed. Nonclassic CAH, which appears later, can also be confirmed with genetic testing because it’s linked to changes in a specific gene called CYP21A2.

A diagnosis of CAH can be confirmed with a genetic test, while there’s no specific genetic test for PCOS.

Genes play a more complex role in PCOS, which can also have environmental and lifestyle causes. There are no specific genetic tests to diagnose PCOS.

2. Beyond Androgens, Different Hormones Are Affected

Both PCOS and CAH involve high levels of androgens, but they affect other hormones differently.

For example, some people with PCOS may have high levels of cortisol, a stress hormone. Too much cortisol can cause symptoms like irregular or missed periods, weight gain around the belly, and hirsutism.

CAH often causes low cortisol because the adrenal glands are missing an enzyme that helps make this hormone. Low cortisol can lead to fatigue, low appetite, and low blood pressure.

3. CAH Affects People of All Sexes

PCOS originates in the ovaries, organs that produce and release eggs, as well as hormones related to reproduction and sexual development. CAH, on the other hand, involves the adrenal glands — small glands located above each kidney that everyone has. These glands help control hormones involved in growth, stress response, and metabolism.

4. CAH and PCOS Have Different Treatments

Because CAH and PCOS have different causes, they also have different treatments, so it’s important to get an accurate diagnosis.

CAH and PCOS have very different treatments, which is why it’s important to get an accurate diagnosis.

PCOS treatment often starts with lifestyle changes, like improving nutrition and being more active. Hormonal birth control may be prescribed to help regulate the menstrual cycle and reduce symptoms like excess hair growth or acne. Other medications may help your body process insulin or block the effects of androgens to ease certain PCOS symptoms.

Nonclassic CAH may not need treatment, but birth control or medications to block the effects of androgen may be prescribed. Glucocorticoids may also be used for people with mild symptoms.

Classic CAH needs close monitoring and treatment as early as possible — usually starting at birth — to support healthy growth and development. Treatment may involve several medications, including daily glucocorticoids.

Talk With Your Doctor

PCOS and nonclassic congenital adrenal hyperplasia don’t always cause symptoms. For many people, signs might not appear until adolescence or adulthood. Some don’t realize they have one of these conditions until they notice irregular periods or have trouble getting pregnant.

Let your healthcare provider know if you notice symptoms that could indicate PCOS or nonclassic CAH, such as irregular periods, hirsutism, hair loss, or fertility problems. These can be signs of PCOS, NC-CAH, or another hormone-related condition. Your doctor can order tests to help figure out what’s going on and suggest treatments that fit your needs.

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