Is It PCOS or Cushing's? How to Tell the Difference

If you have been diagnosed with Polycystic Ovary Syndrome (PCOS) but are experiencing symptoms like severe muscle weakness or rapid body changes, you may be wondering if you actually have Cushing’s. PCOS and Cushing’s can look very similar, but they require entirely different diagnostic approaches.

First, it helps to understand the terminology. Cushing’s syndrome refers to having too much cortisol (the body’s stress hormone) in your system from any cause—including taking steroid medications or having an adrenal tumor. Cushing’s disease is a specific type of Cushing’s syndrome caused by a pituitary tumor. When comparing symptoms with PCOS, doctors are generally looking for signs of Cushing’s syndrome.

While both conditions can cause weight gain, irregular periods, excess body hair, and acne ^[1][2], the key difference lies in the rapid onset of symptoms and the presence of “red flag” features that are highly suggestive of prolonged cortisol excess ^[3]. If your symptoms are atypical for PCOS, you should talk to your doctor about specific screening tests to evaluate your cortisol levels ^[4][5].

The Overlap: Why Confusion Happens

It is easy to see why these two conditions are sometimes confused. Research shows that almost half (46%) of patients with Cushing’s syndrome experience features that mimic PCOS ^[6]. These include menstrual dysfunction, insulin resistance, and hyperandrogenism (excess androgens, which are hormones present in people of all sexes that can cause unwanted hair growth and acne when elevated) ^[6].

In both conditions, you might notice stubborn weight gain and changes to your skin ^[7]. When diagnosing PCOS, doctors use established criteria and consider other conditions that mimic it. While routine Cushing’s testing isn’t necessary for every person with PCOS, it is an important step for those who develop highly suggestive or atypical symptoms ^[3][2].

Atypical “Red Flags” Suggesting Cushing’s

Cushing’s syndrome is rare, but you should look for signs of cortisol excess that are not typically seen in PCOS. No single symptom proves you have Cushing’s, but if you notice the following features, it may prompt your doctor to investigate further:

• Rapid, Central Weight Gain: While PCOS often causes gradual weight gain, Cushing’s is frequently characterized by rapid weight gain that centers intensely around the abdomen, chest, and face, often leaving the arms and legs relatively thin ^[1][4]. You may also notice a fatty hump at the base of the neck or a rounded, flushed face ^[4].
• Severe Proximal Muscle Weakness: Proximal muscles are those closest to your core, such as your thighs, hips, and shoulders. You might find it suddenly difficult to climb stairs, rise from a low chair without using your arms, or lift your arms above your head ^[4][8][9]. This marked weakness is a strong clue for Cushing’s.
• Skin Changes and Easy Bruising: High cortisol significantly thins the skin. You may bruise very easily from minor bumps, or notice that small wounds take an unusually long time to heal ^[4][8].
• Wide, Purple Striae (Stretch Marks): Stretch marks from simple weight gain are usually pale, silver, or light pink. In contrast, Cushing’s can cause striae (stretch marks) that are typically wide—more than 1 centimeter across—and deep red, purple, or violaceous, most often appearing on the abdomen, breasts, hips, or underarms ^[4][8].
• Additional Clues: Unexplained bone fractures or thinning bones at a young age ^[10][11], new or difficult-to-control hypertension ^[12], and severe insomnia ^[13] can also accompany Cushing’s. While these can happen for other reasons (like sleep apnea or mood disorders), they are important pieces of the clinical puzzle.

Symptom Comparison

Testing to Tell the Difference

Before ordering lab tests, your doctor should review all of your medications. The most common cause of Cushing’s syndrome is exposure to exogenous glucocorticoids (steroids like prednisone, hydrocortisone, or dexamethasone) in the form of pills, injections, inhalers, or skin creams ^[14]. Safety Warning: Never stop taking prescribed steroid medications abruptly without medical supervision, as doing so can be dangerous.

If external steroids are ruled out, a standard morning cortisol blood test or basic hormone panel is not enough to accurately screen for Cushing’s ^[15]. Instead, your doctor will likely recommend one or more of these first-line screening tests ^[16]:

• Late-Night Salivary Cortisol (LNSC): You collect a saliva sample at home right before bed. Elevated nighttime cortisol is a strong indicator of Cushing’s ^[13][17]. Doctors often ask for samples on two separate nights.
• 24-Hour Urinary Free Cortisol (UFC): You collect all of your urine for a full 24 hours to measure total daily cortisol production ^[16][13]. Usually, this is also done twice.
• 1-mg Overnight Dexamethasone Suppression Test (DST): You take a low dose of a steroid pill late at night, and your blood cortisol is drawn the next morning to see if your body appropriately suppressed its own cortisol production ^[5].

Understanding Your Results

Testing for Cushing’s is complex, and results must be interpreted carefully:

• Medication interference: Oral birth control pills containing estrogen increase cortisol-binding proteins and can cause falsely elevated results (especially on the DST), but you should not stop taking them without medical advice ^[18][19].
• Other factors: An incomplete 24-hour urine collection will cause a falsely low result ^[13]. Conversely, severe acute stress, major illness, or kidney disease can artificially raise cortisol levels ^[19].
• Next Steps: An abnormal screening result does not instantly prove you have Cushing’s. It usually requires confirmation with repeat tests and a referral to an endocrinologist ^[5]. Once excess cortisol is confirmed, the endocrinologist will use further tests—such as measuring your ACTH levels—to determine if the source is a pituitary tumor (Cushing’s disease) or something else ^[20]. Even if tests are normal, your doctor may re-test you later if your symptoms strongly suggest cyclic Cushing’s (where cortisol levels fluctuate over time) ^[19].