Osteoporosis and Its Causes

Updated: June 16, 2022

Osteoporosis means porous bone. It is a disease characterized by low bone mass and loss of bone tissue that may lead to weak and fragile bones.
Bone density decreases after 35 years of age, and bone loss occurs more rapidly in women after menopause.  Healthy bone looks like a honeycomb when viewed under a microscope.
When osteoporosis occurs, the holes and spaces in the honeycomb are much larger than in healthy bone. Osteoporotic bones have lost density or mass and contain abnormal tissue structure. As bones become less dense, they weaken and are more likely to break especially in the hip, spinal vertebrae, and wrist.
It can affect both males and females, but it is most likely to occur in women after menopause.This happens because of the sudden decrease in estrogen during menopause, the hormone that normally protects against osteoporosis.

What is osteoporosis?

Normal bone is composed of protein, collagen, and calcium, all of which give bone its strength. The body maintains bone density and the integrity of its crystals and structure by regularly replacing old, damaged bone by new ones. As we age, bone breaks down faster than it builds. If this happens excessively, osteoporosis results.

Causes and Risk factors:

There are several risk factors associated with osteoporosis. Some are modifiable, but others cannot be avoided.

Unavoidable factors:

Non-modifiable risk factors include:

Age:

Risk of osteoporosis increases after the mid-30s, and especially after menopause in women.

Bone structure:

Being tall (over 5 feet 7 inches) or slim (weighing under 125 pounds) increases the risk.

Fracture history:

Personal history of fracture as an adult especially after the age of 50 years.

Genetic factors:

Having family history of osteoporosis such as a close family member with a diagnosis of hip fracture or osteoporosis makes it more likely.

Ethnicity:

White people and Asians are more susceptible than other ethnic groups.

Low estrogen levels in women:

This may occur in menopause or with early surgical removal of both ovaries. Lower estrogen levels make it harder for bone to reproduce.

Hypogonadism:

Low testosterone levels in men

Diet and lifestyle choices:

Modifiable risk factors include:

• tobacco smoking
• excessive alcohol intake
• inactivity or immobility such as after a stroke, or from any condition that interferes with walking
• low levels or intake of calcium, magnesium, and vitamin D, due to dietary factors, malabsorption problems, or the use of some medications
• eating disorders, such as anorexia or bulimia nervosa, or orthorexia

Weight bearing exercise helps prevent osteoporosis by placing stress on the bones, and there by encouraging bone growth.

Medications and Health Conditions:

Some diseases or medications cause changes in hormone levels. Some medicines also reduce bone mass.
Diseases that affect hormone levels include hyperthyroidism, hyperparathyroidism, and Cushing's disease. Women who receive hormone treatment (HT) may be at higher risk of osteoporosis.

Disease that increase the risk include:

• COPD
• chronic kidney disease
• cancer
• some autoimmune diseases, such as rheumatoid arthritis and ankylosing spondylitis
• Malabsorption (nutrients are not properly absorbed from the gastrointestinal system) from bowel diseases, such as celiac sprue that can be associated with skin diseases, such as dermatitis herpetiformis
• Hyperthyroidism, a condition wherein too much thyroid hormone is produced by the thyroid gland
• Hyperparathyroidism is a disease wherein there is excessive parathyroid hormone production by the parathyroid gland, a small gland located near or within the thyroid gland. Normally, parathyroid hormone maintains blood calcium levels by removing calcium from the bone. In untreated hyperparathyroidism, excessive parathyroid hormone causes too much calcium to be removed from the bone, which can lead to osteoporosis.
• Amenorrhea which is loss of the menstrual period in young women is associated with low estrogen and osteoporosis. This disease can occur in women who undergo extremely vigorous exercise training and in women with very low body fat.

Medications that raise the risk include:

• glucocorticoids and corticosteroids, including prednisone and prednisolone
• thyroid hormone
• thiazide diuretics
• thiazolidinediones, used to treat type 2 diabetes, as these decrease bone formation
• anticoagulants and blood-thinners, including heparin and warfarin
• protein-pump inhibitors (PPIs) and other antacids that adversely affect mineral status
• some immunosuppressant agents, such as cyclosporine, which increase both bone resorption and formation
• some antidepressant medications
• some vitamin A (retinoid) medications
• some chemotherapeutic agents, including letrozole (Femara), used to treat breast cancer, and leuprorelin (Lupron) for prostate cancer and other conditions
• aromatase inhibitors and other treatments that deplete sex hormones, such as anastrozole, or Arimidex

The most common type of medicine induced osteoporosis is glucocorticoid-induced osteoporosis.