Aging can be defined as any change to an individual over time. It is an inevitable process in human life. There is chronological aging and biological aging, although in general they go in parallel direction. As we age, we experience changes in our physical and psychological states.

There is a steady decline in the function of all body systems, such as the brain, heart, liver, and kidneys. It is associated with:

• Reduced protein synthesis
• Decrease in lean body mass and bone mass
• Increase in percentage of body fat
• Decrease in physical strength
• Decrease in memory and other cognitive functions
• Decrease in the ability to maintain a homeostasis and fight diseases
• Decrease in the overall quality of life.

Theories Of Aging

• Structures at the ends of chromosomes called telomeres have been shown to shorten with each successive cell division. This activates a mechanism that prevents further cell division, and provide a biological clock which will stop when the telomers are lost totally.
• Waste products and cross-linked compounds accumulate inside cells and interfere with metabolism.
• Increase in auto-antibodies that attack the body's tissues.
• Free-radicals, which are unstable and highly reactive organic molecule resulted from oxidation, cause damages to the body systems.
• The endocrine glands are depleted of their production, with a decrease in various hormones such as growth hormone and thyroid hormone.

Anti-aging

Anti-aging addresses how to prevent, slow, or reverse the effects of aging and help people live longer, healthier, happier lives. Many cultures developed long traditions of herbs, foods, diets, and health practices to foster anti-aging. The ultimate goals are to add life to years as well as to add years to life.

The nowadays anti-aging practices includes nutrition, physical fitness, skin care, aesthetic treatments, hormone replacements, vitamins and supplements. These target to give a youthful external appearance, and a strong healthy internal functions.

Bio-identical Hormone Replacement

Out of all the supplements administered into the body, hormones have been studied extensively, and there is much interest today in the use of anti-aging hormones. Many studies have shown a gradual decline in a number of hormones, and this decline may be responsible for some of the effects of the aging process.

Decline in oestrogen and progesterone in menopause for women, and their replacement, has been the subject of much research. Attention now appears to have focused on other hormones. These include:

• human growth hormone (HGH)
• the male hormone testosterone in men, and interestingly women
• the adrenal hormone dehydroepiandrosterone (DHEA)
• the pituitary hormone melatonin.

The decline in these hormones starts much earlier and is more gradual, as early as from 30 years old onwards. The relative deficiency of each of them leads to a variety of symptoms that may be reversed with their replacement.

We shall discuss the properties and applications of the individual hormones in the following sections.