Osteoporosis

Osteoporosis is a disease characterized by low bone mass and structural deterioration of bone tissue, leading to bone fragility and an increased risk of fractures of the hip, spine, and wrist. According to the WHO criteria, osteoporosis is defined by a BMD value as the diagnostic standard.

Cause

During the lifetime, human bones constantly remodel by bone formation and bone resorption. Bone remodeling is completed by two kinds of bone cells, one is osteoclast (abbr. OC), which promotes bone resorption and the other is osteoblast (abbr. OB), which promotes bone formation.

When performing resorption, an irregular edge is formed, which contains a hydrogen ion pump (proton pump), which pushes hydrogen ions out of the cell, leaving the external environment in an acidic state to facilitate the enzymes it releases. (Ex: acid phosphayase, proteases, lysosomal enzymes, etc.)

The source of osteoblast is stromal cells in bone marrow. They secrete a large amount of collagen typeⅠ, bone matrix protein( Bone Gla Protein, BGP, Osteocalcin) and alkaline phosphatase. Osteoblasts produce new bone, which becomes new bone after 25-35 days through bone mineralization. The factors that affect both osteoblasts and osteoclasts are numerous. When the function between osteoblasts and osteoclasts loses balance, it will also unbalance bone remodeling, too. Bone loss thereby occurs in clinical trials.

Types

(Ⅰ) Primary

It can also be divided into :

Osteoporosis TypeⅠ (Postmenopausal Osteoporosis)

It usually happens to female due to the drop of estrogen during menopause which speeds up bone loss.

Osteoporosis TypeⅡ (Senile Osteoporosis)

Low Vitamin D synthesis of elders will reduce the ability of stomach calcium absorption. Hypocalcemia increases in PTH, which makes the osteoclast more active, and osteoblast less functional that bone mass decreases while aging (decreases by 0.5% to 1%).

 

(Ⅱ) Secondary

It could happen on man or woman among all age groups. This type accounts for 10% of osteoporosis. The reasons are:

1. Endocrine diseases such as Cushing’s syndrome, low gonadal function, anorexia, HPT, and so on.

2. Long-term use of glucocorticoid which is the most common medicine that induces osteoporosis. The mechanisms of action are:

    • Inhibit calcium absorption in stomach.
    • Reduce estrogen in blood.
  • Calcium loss in kidney.
  • Inhibit the formation of osteoblast

3. Other reasons like stomach diseases, poor nutrition, cancer, hematological diseases, genetic diseases, and so on.