A buffalo hump is a pad of fat that builds up between the shoulder blades at the base of the neck. The most common cause is excess cortisol in the body, a condition known as Cushing syndrome. But several other conditions, from long-term steroid medications to obesity and HIV treatment, can trigger the same kind of fat deposit.
Understanding what’s behind it matters because a buffalo hump is often a visible sign of something systemic happening inside the body, not just a cosmetic issue.
Excess Cortisol and Cushing Syndrome
Cortisol is a stress hormone produced by the adrenal glands. When the body has too much of it for too long, fat begins to redistribute in characteristic ways: around the face (creating a rounded “moon face”), around the midsection, and at the back of the neck. That neck deposit is the buffalo hump.
Cushing syndrome can develop for two main reasons. The first is internal: a tumor on the pituitary gland or adrenal glands drives cortisol production far above normal levels. The second, and more common, cause is external: taking corticosteroid medications at high doses for extended periods. These drugs are prescribed for conditions like asthma, emphysema, rheumatoid arthritis, and lupus. Prednisone, dexamethasone, and hydrocortisone are among the most frequently used. Because these medications mimic cortisol, the body responds to them the same way it would to overproduction from the adrenal glands, redistributing fat to the upper back, face, and abdomen.
If you’ve been on corticosteroids for months and notice a growing fat pad at the base of your neck, that medication is the most likely explanation. The fat accumulation typically develops gradually, and it can partially or fully reverse once the medication is tapered or discontinued, though this isn’t guaranteed.
HIV Treatment and Fat Redistribution
People living with HIV who take antiretroviral therapy sometimes develop a pattern of fat redistribution called lipodystrophy. Fat accumulates in the abdomen and at the back of the neck while thinning in the face, arms, and legs. The classes of HIV medication most associated with this pattern are protease inhibitors and a drug called efavirenz.
The mechanism isn’t identical to what happens with cortisol. These medications appear to interfere with how the body processes and stores fat at a cellular level, leading to abnormal deposits. Newer classes of HIV medication, called integrase inhibitors, are sometimes substituted to reduce this side effect, though they carry their own risk of generalized weight gain. If you’re on HIV treatment and notice changes in where your body stores fat, your provider can evaluate whether a medication switch makes sense.
Obesity and Metabolic Disease
Obesity, particularly central obesity (fat concentrated around the face, neck, and abdomen rather than evenly distributed), can produce a buffalo hump without any underlying hormonal disorder. This is more than a cosmetic overlap. A 2024 study in the Journal of Clinical Medicine examined 12 patients with buffalo humps unrelated to HIV and found striking metabolic profiles: 66.7% had hypertension, 66.7% had diabetes, and 75% had abnormal cholesterol levels. The average BMI was just above 30, placing most patients in the obese range. Three of the twelve were newly diagnosed with a metabolic condition they hadn’t known about.
The researchers concluded that a non-HIV buffalo hump may act as an “externally visible marker of systemic metabolic burden.” In other words, the fat pad at the back of the neck can be a red flag for insulin resistance, high blood sugar, and cardiovascular risk factors, even when overt Cushing syndrome isn’t present. Subclinical cortisol excess (levels that are elevated but not high enough for a formal Cushing diagnosis) may play a role in these cases, though the exact mechanism is still being studied.
This means that if you develop a buffalo hump and you’re overweight but not on steroids or HIV medication, it’s worth getting screened for diabetes, high blood pressure, and cholesterol problems. The hump itself may be the most visible sign of a broader metabolic picture.
Rare Genetic Conditions
Two uncommon conditions also cause buffalo humps. Familial partial lipodystrophy is a genetic disorder that causes the body to distribute fat abnormally from a young age. People with this condition lose fat in some areas (typically the limbs) and accumulate it in others, including the upper back and neck. It’s usually diagnosed in childhood or early adulthood based on family history and the distinctive pattern of fat distribution.
Madelung disease, also called multiple symmetrical lipomatosis, causes large, symmetrical fat deposits around the neck, shoulders, and upper back. It’s rare in the general population and occurs most often in men with a history of heavy alcohol use. The fat deposits in Madelung disease tend to be more diffuse than a single hump, sometimes creating a “horse collar” appearance around the entire neck.
Buffalo Hump vs. Dowager’s Hump
Not every bump at the back of the neck is a buffalo hump. A dowager’s hump, more accurately called kyphosis, is a curvature of the upper spine that creates a visible rounded hump. It’s caused by bone and posture problems: vertebral compression fractures from osteoporosis, degenerative disc disease, or long-term poor posture. The key difference is what you’re feeling. A buffalo hump is soft and made of fat tissue. A dowager’s hump feels bony and firm, and it’s often accompanied by a noticeable forward curve of the upper spine. The two can coexist, especially in older adults, but they have entirely different causes and require different approaches.
How the Cause Is Identified
Because a buffalo hump can signal several different conditions, figuring out what’s behind it usually involves blood work and a physical exam. If cortisol excess is suspected, you’ll typically be asked to provide a urine sample collected over 24 hours or a late-night saliva sample to measure cortisol levels. Blood tests can also check for diabetes, cholesterol abnormalities, and other metabolic markers. If you’re taking corticosteroids or HIV medications, the connection is often straightforward, and your provider will focus on whether adjusting your treatment is possible.
Imaging like CT or MRI scans may be ordered if a pituitary or adrenal tumor is suspected, or if the provider wants to distinguish fat accumulation from a spinal issue.
Treatment Depends on the Cause
There’s no single treatment for a buffalo hump because the approach depends entirely on what’s driving it. If corticosteroid medication is responsible, gradually reducing the dose (never abruptly, which can be dangerous) often allows the fat pad to shrink over weeks to months. If Cushing syndrome is caused by a tumor, treating or removing that tumor addresses the cortisol excess and, in turn, the fat redistribution. For HIV-related lipodystrophy, switching medication classes may slow or partially reverse the process.
When the hump is related to obesity and metabolic disease, weight loss through diet and exercise can reduce it, though spot reduction isn’t possible. The fat pad shrinks as overall body fat decreases. In cases where the hump persists despite addressing the underlying cause, or where it causes significant discomfort or restricted neck movement, surgical removal through liposuction is an option. The fat can recur after surgery if the root cause isn’t also managed.