Before talking about what causes osteoporosis, let’s look at the functions of bones. Bones serve as a large reservoir of calcium and to support the skeletal system. Bones are constantly regenerating as a way to get rid of old bone tissue and strengthen the bones with new bone tissue. It is estimated that the skeleton is completely replaced approximately over 4 years. Bone building, known as “remodeling” is the process of resorption and formation.
- Resorption: In resorption old bone is eaten up by the body (osteoclasts) and calcium, phosphorus, and collagen type 1 are in released into circulation. Osteoblasts are created when the parathyroid hormone stimulates the Osteoblasts, who in turn signal the monocytes and macrophages to differentiate into osteoclasts. Resorption takes days to weeks.
- Bone formation: is when osteoblats lay down new bone tissue called osteoid, which is made up of of type 1 collagen and other proteins. In order for the new bone tissue to grow strong, the osteoblasts deposit calcium and phosphorus (this step depends on the amount of calcium and phosphorus available, which is why it is important that we get enough calcium in our diet.) Bone formation takes months.
Osteoporosis occurs when more bone is being broken down than built up. This can occur due to estrogen deficiency, steroid use, etc. There are two types of osteoporosis; primary and secondary.
Primary osteoporosis is defined when we do not know the cause and is associated with the following:
- Due to aging and/or menopause (around age 40-60)
- More common in women than men
- The risk of primary osteoporosis depends on the thickness of the bones in early life, diet, physical activity, and overall health
- For example; people of Indian decent are known to have thinner bones as compared to those of American or European
Secondary osteoporosis is when we can pin point a cause and is associated with the following:
- Chronic conditions that contribute significantly to accelerated bone loss (Graves disease, alcoholism, cystic fibrosis, celiac disease, parkinsons, MS, lupus, etc)
- Medications (PPI, thyroid medications, heparin, steroids, etc)