Several factors—both biological and environmental factors—affect the formation of your bones as you age.
Biological Factors Involved in Normal Bone Formation
There is a rapid formation of bone mass in the fetus and infant. This slows somewhat during childhood until age 11 in females and a year or so later in boys. During the growth spurt that accompanies adolescence, tremendous bone formation occurs. The vast majority of adult levels of bone mass are achieved by age 18 or so, with only a small amount added until about 28 years old.
There are a number of hormones that are important to this rapid formation of bone during the first two decades of life. These hormones include, estrogen in females, testosterone in males, growth hormone, and some other minor hormones.
Environmental Factors Influencing Normal Bone Formation
There are also some important lifestyle issues that have an effect on the normal formation of bone. Physical activity and good nutrition are the most important of these environmental factors.
People who are affected by any of these factors will likely have a lower bone mineral density (BMD) than their healthier peers:
Remember, it is the difference between how much healthy bone is formed during the first 28 or so years of life and the rate at which it is remodeled and removed later in life that determines the degree of osteoporosis or osteopenia.