The adrenal glands are soft, small (4x1 cm) organs that sit on top of each kidney.  The adrenal glands are made up of two parts: an inner “medulla” and an outer “cortex”.  The cortex and medulla are essentially two different organs with different functions and different diseases.  They will be considered separately in this discussion.

Adrenal Medulla

The adrenal medulla is a gland but it is closely related to the nervous system.  It manufactures adrenalin that most people know is released during episodes of stress.  Adrenalin (and related compounds) are metabolized (broken down) into several substances such as VMA (vanillylmandelic acid), metanephrines, nor-metanephrines, and catecholamines.

These products can be measured to assess stress situations but this use is not recommended because the results are highly variable.

The reason for measuring the adrenalin substances is to diagnose a very rare condition known as Pheochromocytoma.  This is a tumor of the adrenal gland that produces excessive adrenalin products and causes episodes of sweating, rapid pulse, and high blood pressure. The test is performed on a urine collection.

Adrenal Cortex

The adrenal cortex produces steroid hormones.  These are of three types:

• Mineralocorticoids: steroids that are responsible for controlling salt balance (e.g. Aldosterone),
  
• Glucocorticoids: steroids that influence glucose metabolism and the body’s immune system (e.g. Cortisol), and
  
• Androgens: steroids that are anabolic steroids (muscle builders) and mild “male” hormones (e.g. Androstendione, DHEA).

There are several disorders that may be the result of increased or decreased production of these hormones.

Cushing’s Syndrome

If the adrenal gland produces too much Cortisol because of an adrenal gland abnormality or because of pituitary overactivity then Cushing’s Syndrome appears.  Patients with Cushing’s have increased body fat with thin limbs, a flushed and swollen face (moon face), hypertension, a diabetic tendency, and osteoporosis.  Such patients have a raised serum Cortisol that must be measured with a timed blood sample. If Cushing’s Syndrome is strongly suspected an overnight dexamethasone test can be done.  The patient is asked to take 0.5 mg of dexamethasone tablets before going to sleep. The next morning they go to the lab where a blood sample is drawn for Cortisol.  Normally, the dexamethasone will cause the Cortisol to fall to very low levels. Patients with Cushing’s Syndrome resist the drug and do not show the required fall. Depending on the results of this test, further testing with more elaborate protocols is undertaken.  The most common reason for Cushing’s is taking the drug Prednisone.  Testing is not usually required in this case.

Addison's Syndrome

If the adrenal glands fail or if the pituitary gland does not work then the patient is unable to produce enough Cortisol, then Addison’s syndrome occurs.  Patients with Addison’s have exhaustion, weakness, low blood pressure, and may develop dark pigmentation.  Such patients have unusually low serum Cortisol levels. To confirm the diagnosis an ACTH stimulation test can be carried out. The patient is given an injection of synthetic ACTH that causes the normal adrenal gland to make Cortisol.  Thus, the blood level of Cortisol rises.  In Addison’s Syndrome, the Cortisol will fail to rise to expected levels.

Aldosteronism

If the adrenal gland produces too much aldosterone, then Conn’s Syndrome may be the cause.  Patients with Conn’s Syndrome have high blood pressure.  Special testing of aldosterone is required to make the diagnosis.  These tests are carried out in conjunction with measurements of urine sodium and may require special salt diets, withdrawal of drugs, or lying and standing blood measurements.

Adrenal Imbalance (21-hydroxylase defect)

If there is a defect in the adrenal enzyme known as 21-hydroxylase, the normal adrenal production of hormones may go out of balance.  This may cause excessive androgens to be produced and these cause acne and excessive body and facial hair in women.  A 17-OHP test can be done to help diagnose the condition.  A Stimulation Test provides a more definitive diagnosis.