According to the U.S. Centers for Disease Control and Prevention (CDC), 5 to 20 percent of Americans contract the influenza (flu) virus each year. Flu produces a spectrum of disease, ranging from mild, self-limited respiratory disease to life-threatening pneumonia.

Creatinine comes from your body's everyday use of your muscles -- and also from eating meat. As blood flows through the kidneys, creatinine is excreted out into your urine along with other waste products.

While your weight can be a reflection of your current state of health, your height usually isn't. According to "Scientific American," 20 to 40 percent of your height is determined by environmental factors like nutrition, but 60 to 80 percent is determined by genetics.

New discoveries about how the body's systems function and work together continue to emerge almost daily. However, a very basic and fundamental understanding of the body's integrated working parts and organ systems has been in place for centuries.

Blood sugar, or glucose, serves as the fuel your body uses to generate energy. The level of glucose in your blood remains fairly stable, slightly rising after eating and declining a small amount between meals or after exercising. Blood glucose can be measured in many ways.

The female reproductive system is primarily regulated by five hormones including estrogen, progesterone, gonadotropin releasing hormone, follicle stimulating hormone, and luteinizing hormone. These hormones play a role in one or more stages of development and function of the female reproductive system.

Red, blotchy facial skin is unsightly and can be uncomfortable, depending on the cause of the blotches. When blotches suddenly appear on your face, an allergic reaction or skin condition may be to blame. Your doctor can prescribe an appropriate treatment to clear up red skin blotches and ease any accompanying itching.

You've probably often heard the guideline that you should drink at least eight 8-oz. glasses of water each day. Everyone knows that water is necessary for life and good health, but the actual effects of water on the human body may not be so clear.

Posture is the position you maintain while standing, sitting or lying down. You have good posture when your position creates the least amount of strain on supporting muscles and ligaments when you move or perform weight-bearing activity.

When it comes to making babies, women do the heavy lifting. The parts of the female reproductive system work together in a symphony of function that starts with fertilization and culminates in the birth of a baby.

Gold is more than just an expensive yellow metal. It has been exploited by physicians for decades to treat rheumatoid arthritis, asthma and a variety of other disorders.

If you feel bloated and gassy regularly, you’re not alone -- 10 to 20 percent of adults complain of gas in the form of belching or flatulence, and it’s normal to emit flatus 12 to 25 per times day, according to Brigham and Women’s Hospital.