Adrenal glands: Adrenals -- have hormones will travel

By: BRADLEY J. FIKES - Staff Writer | Saturday, August 12, 2006 6:47 PM PDT ∞

The adrenal glands are the body's chemical beehive, a factory of hormones that help us respond to stress, shape our gender, control our body's daily rhythms; the beehive also regulates the level of water, sodium and potassium.

Perched on top of the kidneys, the adrenal glands secrete dozens of hormones to perform all these tasks. Epinephrine, also known as adrenaline, is the best-known of these hormones.

It prepares us to confront danger by increasing heart rate, increasing blood sugar, dilating lung passages called bronchi and redirecting blood from the digestive organs to the heart, liver, brain and skeletal muscles.

This is useful in facing a physical threat: For strenuous exertion, you need more blood flow of energy-bearing glucose to your legs and arms, and more oxygen. However, the power of adrenaline and other adrenal stress hormones carries a long-term cost.

Adrenaline suppresses the immune system in the short term, and repeated stress can make this immune suppression chronic.

Another stress hormone, cortisone, has been linked with anxiety-related depression in a study performed by researchers at Harvard Medical School. and its affiliate, McLean Hospital.

The study was performed on mice given corticosterone, which performs the role of cortisone in rodents. Exposure to corticosterone provided in drinking water for 17 or 18 days produced mice that appeared more fearful than mice tested within one day of being given a dose.

Other lines of evidence were given in the study, published in the April issue of Behavioral Neuroscience. For example, more than half the people with Cushing's disease, caused by too much cortisol, have depression and anxiety.

People getting corticosteroid therapy also have an increased incidence of mood disorders, including anxiety and depression.

Too little of the adrenal hormone cortisol causes Addison's disease, marked by weight loss, weakness, fatigue and low blood pressure. It's treated with replacement hormones given in pill forms. John F. Kennedy was the most famous Addison's patient.

The lesser-known effects of stress could include cravings for comfort food, according to studies such as one published in the February 2002 edition of the American Journal of Physiology.

That study found that late-night snacking could be linked to being overstressed. Compared to those who don't eat at night, patients showed disrupted production of the adrenal hormone cortisol, along with ACTH, a hormone made by the pituitary gland that stimulates production of cortisol.

The increased appetite can also lead to a widening belly, according to a study published in September 2003 in the Proceedings of the National Academy of Sciences. One day after exposure to stress, rats began eating high-energy foods.

When continually subjected to stress, the rats begin getting fat in the abdomen, and the damaging effects of stress are reduced. The researchers, from UC San Francisco, think the fat deposits give a chemical signal that counters the effects of stress.

The close relationship between the adrenal glands and stress has been known for decades. But more recently, the glands have also been found to function as a body clock, along with the main body clock already known to exist in the brain.

Exposure to light sparks genetic activity in the adrenal glands arising from the master body clock. Called the suprachiasmatic nucleus, or SCN, this master clock is located in the hypothalamus.

The activity is accompanied by a surge in corticosterone in the rodent's brain and blood. This was reported in the November issue of the journal Cell Metabolism.

Newer research suggests the adrenals can act independently of any signal from the hypothalamus.

The adrenal glands of rhesus macaque monkeys contain more than 300 genes whose activity varies according to a 24-hour cycle, according to scientists at Oregon Health & Science University. Moreover, some of these same genes are also active in the SCN.

This suggests the adrenals have their own timer, the scientists say. The study was published in the May edition of the journal Molecular Endocrinology.

For patients, this news may help make existing treatments work better, the scientists say. That's because knowledge of the natural rhythm of hormone secretion can help time dosages to produce the best effects with the fewest side effects.

Contact staff writer Bradley J. Fikes at bfikes@nctimes.com or (760) 739-6641.

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