Secondary high blood pressure: When another condition causes hypertension

When something goes wrong in one part of your body, a ripple effect can create problems elsewhere — such as high blood pressure (hypertension). In fact, 5 percent to 10 percent of high blood pressure cases are caused by an underlying condition, according to the American Heart Association.

This type of high blood pressure, known as secondary hypertension, tends to appear suddenly. But there's good news. Proper treatment can often control or cure both the underlying condition and the high blood pressure, which reduces the risk of serious complications — including heart disease, kidney failure and stroke.

Here's a look at possible causes of secondary hypertension.

Marijuana 101: The plant and its components

Marijuana refers to the dried flowers, leaves, stems and seeds of the Cannabis sativa plant. These parts contain the compounds that produce the mind-altering effect that recreational users seek when smoking or ingesting the plant — but they also provide components with potential medical benefits.

Marijuana contains at least 60 chemicals called cannabinoids. Researchers are evaluating how effective some of these cannabinoids might be in controlling symptoms of certain medical conditions. For example:

• THC. An abbreviation for delta-9-tetrahydrocannabinol, THC is the main component responsible for marijuana's mind-altering effect. It also may help treat signs and symptoms such as nausea and vomiting that are associated with a number of medical conditions.
• Cannabinol and cannabidiol. These compounds have some of the properties of THC, but cause less psychoactive effects — the high.
• Dronabinol (Marinol). Dronabinol (dro-NAB-in-ol) is a man-made version of THC available by prescription. It's used to prevent nausea and vomiting after cancer chemotherapy when other medicines for these side effects don't work, and to increase appetite in people with AIDS.

Possible medical uses

Scientists studying marijuana's potential medical uses have found that it may help treat a variety of conditions.

Nausea
One of THC's medical uses best supported by research is the treatment of nausea. It can improve mild to moderate nausea caused by cancer chemotherapy and help reduce nausea and weight loss in people with AIDS.

Younger people may find marijuana more useful as a treatment for nausea than do older people — who may not tolerate its mind-altering side effects as well. The prescription form, dronabinol, also may produce psychological side effects that make it inappropriate for some older people. Doctors generally prescribe several kinds of newer anti-nausea drugs with fewer side effects before resorting to dronabinol.

Glaucoma
This disease — the third-leading cause of blindness in the United States — is marked by increased pressure in the eyeball, which can lead to vision loss.

In the early 1970s, scientists discovered that smoking marijuana reduced pressure in the eyes. Exactly how the cannabinoids in marijuana produce this effect isn't known. Scientists have discovered CB1 receptors in the eyes, which may provide clues for future research on how marijuana affects glaucoma.

Your doctor can prescribe other medications to treat glaucoma, but these can lose their effectiveness over time. Researchers are working to develop medications containing cannabinoids that can be put directly on the eyes — to avoid the mind-altering side effects and other health consequences of smoking the plant.

Pain
People widely used marijuana for pain relief in the 1800s, and several studies have found that cannabinoids have analgesic effects. In fact, THC may work as well in treating cancer pain as codeine, a mild pain reliever. Cannabinoids also appear to enhance the effects of opiate pain medications to provide pain relief at lower dosages.

Researchers currently are developing new medications based on cannabis to treat pain.

Multiple sclerosis
Research results on the effectiveness of cannabinoids in the treatment of the tremors, muscle spasms and pain of multiple sclerosis (MS) — a disease of the nervous system that can cause muscle pain — are mixed. A 2003 study found that cannabinoids significantly reduced pain in people with multiple sclerosis.

Some scientists feel that more research may show cannabinoids useful in treating MS. Marijuana may protect nerves from the kind of damage that occurs during the disease. They also suggest that animal study results, knowledge of CB1 receptors in the brain and users' reports of decreased symptoms after using marijuana support this possibility. However, others advise caution in using marijuana to treat MS, given the modest therapeutic effects cannabinoids have demonstrated so far and the potential of long-term adverse side effects.