What is Cushing’s Disease and How Is It Treated

Cushing disease is a rare condition in which there is too much cortisol hormone in the body. It is a specific type of condition called Cushing’s syndrome. According to the National Institute of Diabetes and Digestive and Kidney Diseases, Cushing disease occurs in 40-70 people out of every million. Please continue reading to learn more about what causes Cushing disease and how it is diagnosed and treated.

What is the pituitary gland, and what are the adrenal glands?

To understand Cushing disease, we first need to understand how certain glands in the body function. The pituitary gland is a small pea-sized gland located at the base of the brain. It is part of the body’s endocrine system and makes many essential hormones, such as the adrenocorticotropic hormone (ACTH). ACTH and other pituitary hormones regulate other endocrine glands in the body, such as the adrenal glands, thyroid gland, and reproductive organs like the testes and ovaries.

The adrenal glands are a pair of small glands. There is one adrenal gland on top of each kidney. The adrenal cortex and adrenal medulla produce hormones that regulate important bodily functions such as blood pressure, metabolism, the immune system, and the body’s response to stress.

The adrenal glands make hormones in response to signals from the pituitary gland, which responds to a part of the brain called the hypothalamus. These structures are together called the hypothalamus pituitary adrenal axis. They control cortisol levels and play an important role in the development of Cushing disease.

If the pituitary gland makes too much adrenocorticotropic hormone (ACTH), this sends a signal to the adrenal glands to make more cortisol. When the adrenal glands produce cortisol in excess, it cause the signs and symptoms of Cushing disease.

What causes Cushing syndrome?

The following can be responsible for causing Cushing syndrome:

The use of corticosteroid medications, such as prednisone, to treat chronic conditions like rheumatoid arthritis and lupus.
Pituitary tumors (benign pituitary adenomas) which lead to high ACTH levels. This causes overactive adrenal glands and excess cortisol production.
Adrenal tumors that secrete adrenal hormones such as cortisol.
Ectopic tumors located outside the pituitary gland that secrete ACTH. This is called ectopic ACTH syndrome or ectopic Cushing syndrome. The ectopic tumor can be in the lungs, thyroid, thymus, or pancreas.

What is the difference between Cushing's syndrome and Cushing's disease?

Cushing syndrome is a condition in which there is too much cortisol in the body. It is also called hypercortisolism. The high cortisol levels can be from endogenous (internal) or exogenous (external) sources. For example, cortisol production in the body may be high because of an adrenal tumor or pituitary tumor (endogenous cause). Cortisol levels can also be high because of corticosteroid medications (exogenous Cushing syndrome).

Cushing disease is a type of Cushing syndrome. It occurs when a benign tumor in the pituitary gland makes too much ACTH (adrenocorticotropic hormone). This causes the adrenal glands to make too much cortisol. Cushing disease accounts for 7 out of 10 endogenous Cushing’s syndrome cases.

How does Cushing's make you feel?

As mentioned, people with Cushing’s syndrome have too much of the hormone cortisol in their bodies. It is called the stress hormone and it plays an important role in the body’s stress response (the body increases cortisol production in times of stress). Cortisol helps to increase heart rate and blood pressure, regulate respiration and blood sugar levels, and increase muscle tension in times of stress. Once a stressful situation is over, cortisol levels fall. However, if cortisol levels remain high, for example, due to cortisol produced by the adrenal glands in response to ACTH from a pituitary tumor, it causes the symptoms of Cushing disease. Cushing syndrome symptoms are therefore related to excess cortisol in the body.

What are the signs and symptoms of Cushing syndrome?

The signs and symptoms of Cushing’s can include:

Rapid weight gain, especially on the face, neck, abdomen, and back. It causes a red, round face, sometimes called a moon face, as well as weight gain on the back and neck, sometimes referred to as a buffalo hump.
High blood pressure.
Poor wound healing.
Excessive hair growth or balding.
Diabetes (high blood sugar levels).
Easy bruising.
Purple striae (stretch marks) on the abdomen.
Fatigue and weakness.
Blurry vision.
Dizziness.
Thin arms and legs.
Muscle weakness.
Changes in sex drive.
Erectile dysfunction.
Irregular menstrual periods.
Slowed growth in children.

How do doctors diagnose Cushing syndrome?

It can be challenging to diagnose Cushing syndrome because many signs and symptoms, such as weight gain and fatigue, are nonspecific and can be present in many other conditions. Your doctor will obtain a careful history, perform a physical exam, and order blood tests and other tests to make a diagnosis. Some of the tests they may order include:

24-hour urinary cortisol to measure cortisol levels in the urine.
Midnight salivary cortisol test (cortisol levels are typically the lowest at midnight but may be high in people with Cushing syndrome).
ACTH blood test. A high ACTH level in a blood sample may indicate a pituitary or ectopic tumor.
Low-dose dexamethasone suppression test. This involves challenging your body with a corticosteroid (dexamethasone) dose at night and measuring cortisol levels in the morning. In people with Cushing syndrome, the adrenal glands do not get suppressed by the dexamethasone dose, and cortisol levels remain high.
High-dose dexamethasone suppression test. This is done if the low-dose test is positive. It can tell the difference between a pituitary adenoma (Cushing disease) and an ectopic tumor (for example, in the lungs).

What is the treatment for Cushing syndrome?

Treatment for Cushing syndrome depends on the cause. For example, if the underlying cause of too much cortisol in your body is corticosteroid medications, your doctor will lower the dose or change you to a non-steroid medicine.

If you are not taking steroid medicines, your doctor will look for other causes of too much cortisol, such as a tumor in the pituitary gland or adrenal glands. This can be accomplished with imaging studies such as MRI and CAT scans.

If you have endogenous Cushing syndrome due to a tumor, it can be treated with chemotherapy, radiation therapy, or surgery to remove pituitary tumors or adrenal tumors. Sometimes, it may be necessary to have the adrenal glands removed partially or fully. This can lead to adrenal insufficiency, and you may need to take steroid replacement.

What is the life expectancy with Cushing syndrome?

Cushing syndrome and Cushing disease can be fatal within 4 to 5 years without treatment. Too much cortisol in the body can lead to complications such as infections, blood clots, high blood pressure, diabetes, high cholesterol, heart attack and stroke, weight gain, depression, weak bones and fractures, and cognitive problems.

However, with treatment, survival rates for people with Cushing syndrome and Cushing disease are excellent. Studies have found that people with Cushing disease live for an average of 40 years after curative surgery for pituitary tumor removal.

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