Cushing's Syndrome

Cushing's syndrome is the clinical consequence of prolonged glucocorticoid excess, whether exogenous (prescribed steroids) or endogenous (autonomous cortisol or ACTH production).

The HPA axis, in one sentence: hypothalamic CRH drives pituitary ACTH, which drives adrenal cortisol, which feeds back to suppress CRH and ACTH. In Cushing's, this loop is broken at one of three anatomical points:

• Pituitary — an ACTH-secreting adenoma (Cushing's disease, ~70% of endogenous cases)
• Ectopic — a non-pituitary tumor (small cell lung, bronchial carcinoid, pancreatic NET, medullary thyroid) secreting ACTH
• Adrenal — an autonomously hypersecreting adrenal adenoma or, less commonly, carcinoma; ACTH-independent and suppressed

Why the body breaks down: cortisol excess drives lipogenesis centrally with peripheral lipolysis (central obesity + thin limbs), induces insulin resistance and hepatic gluconeogenesis (diabetes), suppresses osteoblast function (osteoporosis), drives sodium retention and vascular remodeling (hypertension), catabolizes skin and muscle (striae, proximal myopathy), suppresses gonadotropins (menstrual irregularity, ED), and alters neurotransmission (mood, cognition).

Diurnal rhythm is the fingerprint: normal cortisol peaks at ~8 AM and nadirs around midnight. In Cushing's, the midnight nadir is lost — which is exactly what late-night salivary cortisol and overnight dexamethasone suppression tests exploit.

Presentation is rarely complete. Think patterns — especially "metabolic syndrome that's too much, too fast, in someone too young."

Step 1 — Rule out exogenous first. Review every route: oral, inhaled, nasal, intra-articular, topical, compounded. High-dose or chronic use of any route can cause Cushing's syndrome. If exogenous is confirmed, no further workup needed — taper instead.

Step 2 — Choose an initial screen (Endocrine Society recommends two of these):

• Overnight 1 mg dexamethasone suppression test (DST). 1 mg PO at 11 PM, draw 8 AM cortisol. Normal < 1.8 µg/dL. Pooled sensitivity ≈ 98.6% (Galm 2020 network meta-analysis, 139 studies / 14,140 participants) — the most sensitive single test. Tests HPA-axis feedback integrity, so it picks up the earliest abnormality on the hypercortisolism spectrum.
• Late-night salivary cortisol (LNSC) — two samples on separate nights between 11 PM–midnight. Detects loss of diurnal nadir. Pooled sensitivity ≈ 95.8%. Requires enough cortisol overproduction to overwhelm the normal nighttime trough — a later phenomenon than HPA-axis dysregulation.
• 24-hour urinary free cortisol (UFC) — at least two collections. Integrates cortisol exposure over a day. Pooled sensitivity ≈ 94.0%. Requires CBG saturation, so misses ~20–25% of mild Cushing's (Findling & Raff, JCEM 2005).
• Low-dose (2 mg/day × 2 days) DST for patients with conditions that may cause false positives on the overnight test (estrogens/OCPs, CYP3A4 inducers, alcohol use, severe depression, pregnancy).

The discordance pattern matters. A +DST with a normal LNSC is not a false positive — it's the biochemical signature of mild autonomous cortisol secretion (MACS) / non-neoplastic hypercortisolism. The CATALYST trial (Diabetes Care 2025;48:2012–2020) identified this phenotype in 23.8% of patients with difficult-to-control T2D, and the treatment phase showed an A1C drop from 8.62% → 7.12% with mifepristone vs. minimal change on placebo. The accompanying editorial (Findling & Pivonello, Diabetes Care 2025;48:1994–1997) calls this "a useful paradigm shift." Ralph DeFronzo has proposed adding hypercortisolism as the 9th defect in T2D — the "Noxious Nine."

Step 3 — Confirm and refer. Any abnormal screen → repeat or confirm with a different modality. Once Cushing's is biochemically likely, refer to endocrinology. Don't image before biochemistry — pituitary and adrenal incidentalomas are common and will mislead. For the MACS phenotype, also consider an adrenal CT (CATALYST: 34.7% of DST-positive patients had a structural adrenal abnormality).

Step 4 — Localize (endocrinology):

• Plasma ACTH distinguishes ACTH-dependent (high/inappropriately normal) from ACTH-independent (suppressed <10 pg/mL).
• ACTH-dependent → pituitary MRI; if equivocal, inferior petrosal sinus sampling with CRH stimulation is the gold standard.
• ACTH-independent → adrenal CT.
• Ectopic ACTH → chest/abdomen CT, possibly Ga-68 DOTATATE PET for occult neuroendocrine tumors.

Pitfalls: false positives with depression, alcohol use, poorly controlled diabetes, severe obesity, pregnancy, and estrogen therapy (raises CBG). False negatives in cyclic Cushing's — repeat testing when clinical suspicion is high.

Surgical (first-line for nearly all endogenous cases):

• Transsphenoidal adenomectomy for Cushing's disease. Remission ~80% with an experienced surgeon; requires peri-op glucocorticoid cover and gradual HPA recovery.
• Adrenalectomy (laparoscopic preferred) for adrenal adenoma/carcinoma. Bilateral adrenalectomy reserved for refractory ACTH-dependent disease.
• Resection of ectopic source when localized.

Radiation: stereotactic radiosurgery or fractionated radiotherapy for residual or recurrent pituitary disease — effective in 40–85% but takes months to years; requires bridging medical therapy.

Medical therapy (for surgical nonresponders, preop optimization, or when surgery isn't feasible):

• Steroidogenesis inhibitors: ketoconazole, metyrapone, osilodrostat, levoketoconazole, etomidate (ICU only)
• Pituitary-directed: pasireotide (SOM-230), cabergoline (second-line)
• Glucocorticoid receptor antagonist: mifepristone (Korlym) — blocks peripheral cortisol action; useful for hyperglycemia in Cushing's when surgery has failed. Does NOT lower cortisol levels, so lab monitoring shifts to clinical endpoints.
• Adrenolytic: mitotane — reserved for adrenocortical carcinoma

Exogenous Cushing's: gradual steroid taper under medical supervision; never stop abruptly — risk of adrenal crisis. Consider steroid-sparing alternatives when possible.

Post-treatment: the "Cushing's tail" — patients often remain symptomatic for months to years after biochemical remission. Bone density, cardiovascular risk, and mental health all need continued attention.

• Nieman LK, Biller BM, Findling JW, et al. The diagnosis of Cushing's syndrome: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2008;93(5):1526-1540.
• Nieman LK, Biller BM, Findling JW, et al. Treatment of Cushing's Syndrome: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2015;100(8):2807-2831.
• Fleseriu M, Auchus R, Bancos I, et al. Consensus on diagnosis and management of Cushing's disease: a guideline update. Lancet Diabetes Endocrinol. 2021;9(12):847-875.
• Lacroix A, Feelders RA, Stratakis CA, Nieman LK. Cushing's syndrome. Lancet. 2015;386(9996):913-927.
• Buse JB et al. Prevalence of hypercortisolism in difficult-to-control type 2 diabetes (CATALYST prevalence phase). Diabetes Care. 2025;48(12):2012–2020.
• Findling JW, Pivonello R. Unmasking hypercortisolism in difficult-to-control type 2 diabetes: a useful paradigm shift? Diabetes Care. 2025;48(12):1994–1997.
• DeFronzo RA. The Noxious Nine — hypercortisolism as the 9th defect in type 2 diabetes. HCPLive commentary series, 2025.
• Galm BP, Buckless C, Swearingen B, et al. The accuracy of biochemical tests for the diagnosis of Cushing's syndrome — systematic review and network meta-analysis. Endocr Rev. 2020.
• Prete A et al. Cardiometabolic disease burden and steroid excretion in benign adrenal tumors. Ann Intern Med. 2022;175(3):325–334.
• Fassnacht M et al. European Society of Endocrinology clinical practice guideline on the management of adrenal incidentalomas. Eur J Endocrinol. 2023.
• Findling JW, Raff H. Cushing's syndrome: important issues in diagnosis and management. J Clin Endocrinol Metab. 2005;90(7):3746–3753.
• Brosolo G et al. Hypercortisolism and the prothrombotic state. 2024.
• Musolino M et al. Hypercortisolism in hypertension. 2025.
• Korlym (mifepristone) US Prescribing Information, Corcept Therapeutics, 2019.

Cushing's doesn't feel like one thing. Most patients describe it as a slow, confusing pile-up of symptoms that don't seem related — until someone finally connects them.

Your body changes, and it's not your fault. Weight gathers around your belly, face, and shoulders even as your arms and legs get thinner. The scale climbs no matter how strict the diet or how hard the workout. Skin thins and bruises from small bumps. Purple stretch marks show up on the belly, thighs, breasts, or arms.

Energy and strength quietly fade. Climbing stairs gets hard. Getting up from a chair or out of a car takes effort. Holding a glass feels heavier than it should. You're exhausted but you can't sleep.

Your mind changes too. Mood swings, short temper, anxiety, or a kind of depression that doesn't match anything happening in your life. Memory slips. Concentration fails. Some patients describe it as a "fog" that only lifts after treatment.

Other things can go wrong at the same time. Blood pressure rises and needs multiple medications. Blood sugar climbs — sometimes new diabetes shows up suddenly. Periods become irregular or stop. Men can lose sex drive or develop ED. Bones thin, and fractures can happen from minor falls.

Cushing's is often missed for years. Not because doctors are careless — but because the symptoms look like so many other things:

• Weight gain and fatigue are very common
• High blood pressure and diabetes are very common
• Depression and anxiety are very common
• Irregular periods or hair changes can look like PCOS

Individually, each piece gets treated on its own. Nobody steps back and asks, "could one thing be causing all of these?" That's the diagnostic gap.

What helps you get there faster:

• Bring a written symptom list to your appointment. Include every system — not just weight
• Bring side-by-side photos from before things changed and now
• Ask your primary care doctor about screening for Cushing's syndrome. The tests are simple (a saliva sample, a urine collection, or an overnight pill and morning blood draw)
• If your diabetes or high blood pressure is hard to control despite multiple medications, explicitly ask whether Cushing's could be part of the picture
• Ask for a referral to an endocrinologist if screening is abnormal

Cushing's happens when your body is exposed to too much cortisol for too long. The "too much cortisol" can come from two places:

From outside the body (exogenous). This is by far the most common cause. Taking steroid medicines — prednisone, dexamethasone, high-dose inhalers, steroid injections, or certain topical steroids — for weeks to months can cause Cushing's symptoms. If you've been on long-term steroids, talk to your doctor before stopping them. Stopping abruptly can be dangerous.

From inside the body (endogenous). This is rarer. A small growth somewhere in your body is making excess cortisol or excess ACTH (the hormone that tells the adrenal glands to make cortisol). The growth is almost always benign, not cancer, but it still needs treatment. The three possible locations:

• Pituitary gland (at the base of the brain) — this is the most common type. When the growth is here, it's called Cushing's disease.
• Adrenal glands (on top of the kidneys) — a growth here makes cortisol directly.
• Somewhere else — rarely, a growth in the lungs or elsewhere makes ACTH, which fools the adrenals into overproducing cortisol.

Your care team will do testing to figure out which of these is happening. That answer determines your treatment.

The testing usually happens in stages — it's not one visit and done.

Screening tests (to find out if cortisol is genuinely too high):

• Late-night salivary cortisol — you spit into a small tube at bedtime, at home, on two different nights
• 24-hour urine collection — you save all your urine for a full day
• Overnight dexamethasone suppression test — you take a pill at 11 PM and get blood drawn at 8 AM the next day

These tests can be ordered by your primary care doctor. If results are abnormal, you'll be referred to an endocrinologist.

Testing to find the cause:

• More blood tests (including ACTH)
• Imaging — pituitary MRI, adrenal CT, or a chest/abdomen scan depending on what the blood tests suggest
• Occasionally, a specialized test called petrosal sinus sampling to confirm the source is the pituitary

Mild and cyclic Cushing's can be tricky. Cortisol levels may fluctuate and occasionally test normal. If your testing is normal but your symptoms fit, ask whether repeat testing or a Cushing's specialist is appropriate.

Surgery is usually the first choice for endogenous Cushing's. Depending on the source:

• Pituitary tumor → transsphenoidal surgery (through the nose) by a specialized neurosurgeon
• Adrenal tumor → laparoscopic adrenal surgery
• Other source → surgery wherever the growth is

Most people do well after surgery, but recovery takes time. The body has to relearn how to make cortisol on its own, and you may need to take replacement steroid (hydrocortisone or prednisone) for weeks, months, or occasionally longer.

Medications can help lower cortisol or block its effects when surgery isn't possible, isn't enough, or while waiting. Options include medications like ketoconazole, metyrapone, osilodrostat, pasireotide, and mifepristone (Korlym). Your endocrinologist will match the medication to your situation.

Radiation can help after surgery if some tumor tissue remains. It works slowly — often over months to years.

If your Cushing's is from steroid medications, the treatment is a careful, gradual taper under your doctor's supervision. Never stop steroids abruptly — this can cause a serious condition called adrenal crisis.

Life after Cushing's: many symptoms improve over weeks to months after cortisol returns to normal — skin heals, energy returns, mood lifts, blood pressure and sugar often improve. Some effects (like bone loss) need ongoing attention. Recovery is real, but it isn't instant. Patients describe feeling "more like themselves" as months pass, though the journey is often longer than expected.

Cushing's is rare, isolating, and often invisible. Connecting with people who have been through it — and organizations built by patients for patients — makes an enormous difference.

A note on loved ones: Cushing's changes how you look, feel, and act. Family and friends often don't understand why you seem different. Sharing this page or a patient brochure can help them see that this is a real medical condition — not a lifestyle failing.