One of the key hormones, our adrenal gland makes is called “cortisol”. This production is directed by a part of our brain called the hypothalamus which makes a hormone called CRH. CRH “tells” your pituitary gland (the master gland in the brain) to make another hormone called ACTH. ACTH then directs the adrenal gland to make cortisol. Cortisol is important because it regulates our blood pressure, metabolism and helps us deal with physical stress.
Sometimes, either tumors or other conditions involving the pituitary gland or the adrenal gland results in your body making too much of the hormone cortisol over time. This is an uncommon condition (40-70 people per million) but it is quite serious because it can lead to health problems such as: progressive weight gain, type 2 diabetes, blood clots, premature heart disease, increased infections, osteoporosis, memory loss and lack of concentration. Other symptoms of Cushing’s syndrome may include: Weight gain in the central part of the body with relatively thin arms and legs, a round face, increased fat around the base of the neck, easy bruising, wide and purple stretch marks on the abdomen and muscle weakness.
Cushing syndrome can also occur if the patient is given too much cortisol for too long. This is: Exogenous Cushing syndrome. Endogenous Cushing syndrome occurs from overproduction of cortisol from our own body. 70% of such cases occurs because of a tiny pituitary tumor or microadenoma. The second most common cause is an adrenal tumor (usually benign tumors “adenoma”). Some tumors that develop outside the pituitary gland (e.g. pancreas, thymus, lungs) can also produce ACTH. This condition is called ectopic ACTH dependent Cushing syndrome and is less common.
How is it diagnosed?
Doctors may order a urine, saliva or blood test to diagnose Cushing syndrome. None of these tests are perfect and so the doctors usually do 2 of the tests to confirm the diagnosis. Measuring a random blood level of cortisol is not useful because the pain or anxiety from the needle stick can cause cortisol levels to go up. Normally the blood cortisol levels go up and down depending on stress level through the day. The best way to determine overproduction of cortisol by the body is to measure it in a 24-hour urine sample. In addition, the blood cortisol levels drop to a very low level in the evening and around midnight in normal people but this does not occur in those with Cushing syndrome. Because it is hard to get blood levels drawn at midnight, your doctor may order to collect saliva sample in a container while you are resting at home at 11 PM. The saliva cortisol levels done by major commercial labs are quite accurate and correlate with blood levels so if salivary cortisol is high at 11 pm, it is abnormal. The third test is called low-dose dexamethasone suppression test (please see our separate blog on this kind of testing). Basically, you will take 1 mg of dexamethasone (a cortisol like medicine) at 11 PM and get blood cortisol level drawn around 8 AM the next morning. In a normal person, this blood cortisol level should be very low but in those with Cushing syndrome, the levels do not drop.
Sometimes, serial measurements are needed before a diagnosis can be made. Once cortisol overproduction is established, your doctor will order blood ACTH level. If it is low, excess cortisol is coming from the adrenal gland. Your doctor will then order a CT scan of the adrenal gland. If the ACTH level is normal or high, the excess cortisol is coming from the pituitary gland or other rare tumors. Your doctor will probably order an MRI of the pituitary gland and may order some other imaging studies. Sometimes more advanced testing (such as pituitary sinus sampling) is needed because the MRI may not be able to pick up some tiny pituitary adenomas that can still cause Cushing syndrome.
Treatment depends on the cause and may include surgery, radiation or cortisol reducing medications.
For those who have pituitary microadenoma causing ACTH dependent Cushing syndrome, referral to a tertiary care center with expertise in pituitary surgery is recommended. The surgical procedure is called transsphenoidal hypophysectomy. The surgeon approaches the pituitary gland using a tiny, specialized surgical instrument inserted into the nostril and alongside the nasal septum. This instrument then penetrates the sphenoid sinus (a hollow space in a bone in the nose) to remove tumor from the pituitary gland, without cutting through the rest of the brain.
For those with adrenal tumors, a laparoscopic procedure allows removal of the tumor with minimal morbidity. It is recommended to consult with his surgeon who is considered an expert in adrenal surgeries (usually an endocrine surgeon or some urologists).
Successful surgery cannot restore normal blood cortisol levels, although the recovery may be somewhat slow and you may need to follow with your endocrinologist to help you through this recovery process. Nevertheless, normalizing blood cortisol levels will help reduce complications of untreated Cushing syndrome (such as diabetes, osteoporosis, infections, heart attacks and strokes).
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