Bone mass is maintained by a process whereby cells breakdown and re-form bone. With age, our bones break down more quickly than they re-form. The primary cause of osteoporosis is increasing age. After the age of thirty, the rate at which bone is absorbed by the body increases, while the rate of bone building decreases. The mineral content of bones decreases and bones become less dense and more fragile. Therefore, the chances of developing osteoporosis increase with age.
• Low Body Weight
People with low body weight have less fat in their body. Fat produces some amount of estrogen (female sex hormone that prevents bone loss) which plays an important role in bone density. Less fat in the body implies lower production of estrogen. Therefore, people with low body weight are at higher risk of osteoporosis. People with Body Mass index (BMI) less than 20 develop osteoporosis earlier than people with normal body weight as they reduce their bone density more rapidly with age.
• Low Estrogen in Women
Women go through several hormonal changes during their lifetime. These hormonal changes vary among women according to their life-cycle, lifestyle, and occurrence of other diseases. In women, when ovaries stop producing estrogen (female sex hormone which prevents bone loss) due to some diseases or due to menopause, the bone mass is reduced. Estrogen is important for new bone production because it supports bone producing cells osteoblasts. Without estrogen, osteoblasts (bone producing cells) can’t produce enough new bone and eventually osteoclasts (bone absorbing cells) overpower them leading to osteoporosis.
• Lack of Calcitonin
Calcitonin is a hormone that helps to maintain normal calcium levels and strengthens the bones. It works to decrease the amount of calcium in blood and increases the amount of calcium to be excreted in the urine. It prevents the intestine from taking up much calcium from food and increases the activity of bone cells osteoblasts. These cells build new bone matrix using calcium from blood, hence blood calcium levels fall. Therefore, deficiency of this hormone calcitonin leads to osteoporosis.
• Overproduction of Parathyroid Hormone
Parathyriod hormone counteracts calcitonin. It works to increase the amount of calcium in blood and decreases the amount of calcium excreted in urine. It also decreases the activity of osteoblasts causing bone break down and releases the calcium present in the bone into blood. Therefore, overproduction of Parathyroid hormone (Hyperparathyroidism) stimulates bone reabsorption and release excess calcium constantly into blood stream causing osteoporosis.
• Overproduction of Thyroid Hormone
Bone is continuously broken down and is replaced by bone building cells. This process is called as Bone remodeling. Each cycle of bone remodeling takes about 200 days to be completed. Overproduction of thyroid hormone hastens the rate of bone remodeling process. If this process happens too rapidly, the bone- building cells may not be able to replace bone fast enough, thus overall rate of bone loss is increased.
• Low Testosterone in Men
Testosterone is a male sex hormone produced in testes. It has a great impact on bone density and helps the body to attain peak bone mass (at the point where bones have maximum strength and density). Usually with age, the testosterone levels in men decrease slowly. However, testosterone levels may decrease abruptly, if prostate cancer is treated surgically or if using drugs that prevent testicles from producing testosterone. Low testosterone levels result in bone loss. Therefore, men with low testosterone are more likely to develop osteoporosis
• Family History of Osteoporosis
Researchers have found that osteoporosis is mostly related to our genes. Genes control bone formation, bone loss, calcium levels and also affect the hormone estrogen. People who have family history of osteoporosis fractures are more prone to fractures in their later life. Therefore, osteoporosis risk is an unwanted inheritance either from maternal or paternal side.
Caucasian and Asian people are more likely to be affected by osteoporosis than Black people. Women with darker pigmentation have more bone mass than women with fairer pigmentation. This is because women with darker pigmentation produce more calcitonin (bone protecting hormone). They can better tolerate the decrease of bone density with aging.
• Absence of Menstrual Period
Studies show that women with absence of menstrual period have less bone mineral content than those with regular cycles. It includes an early or premature menopause or surgical removal of uterus. This condition is associated with faster bone reabsorption because of estrogen deficiency. Menstrual period also gets suppressed in female athletes. The intense training they go through can lead to decreased bone density and risk of osteoporosis, which is known as female athlete triad.
• Hyperthyroidism and Hypothyroidism
An overactive thyroid gland (Hyperthyroidism) produces too much of thyroid hormone. Untreated hyperthyroidism accelerates bone reabsorption and over the time it can lead to osteoporosis. Overproduction of this hormone increases the bone remodeling process resulting in loss of bone mineral density (amount of mineral matter per square centimeter of bones). Medicines that are prescribed to treat an underactive thyroid gland (hypothyroidism) also have the same effect by accelerating the bone reabsorption and cause osteoporosis.
An overactive parathyroid gland (Hyperparathyroidism) produces large amounts of parathyroid hormone. This hormone regulates the amount of calcium that is absorbed from our diet and the amount that is stored in our bones. In hyperparathyroidism bones release excess calcium constantly into blood stream causing osteoporosis.
Although asthma itself does not cause any threat to bone, people suffering from asthma are at a great risk of developing osteoporosis. This is because of the inflammatory medications known as glucocorticoids, which are used for treating asthma. These medications decrease calcium absorption from food and increase calcium loss from the kidneys. Therefore people having asthma are prone to osteoporosis.
Insulin (a hormone released by beta cells in pancreas) promotes bone growth. People suffering from type-1 diabetes have insulin deficiency. This insulin deficiency increases the risk of osteoporosis as bone growth is retarded in them. People suffering from type-2 diabetes are generally overweight and have a sedentary lifestyle due to which their balance factor and co-ordination is much reduced. They are more prone to osteoporotic fractures.
• Gastrointestinal and Liver Diseases
All gastrointestinal diseases such as Billiary cirrhosis, Ulcerative colitis, Irritable bowel syndrome, Celiac disease, and Crohn’s disease cause osteoporosis. The reason is associated with malabsorption of nutrients necessary for bone growth. These diseases prevent the body from absorbing adequate amounts of calcium and vitamin D from food leading to osteoporosis.
People with depression generally have low bone mass. Depression can cause endocrinal changes by release of a hormone (noradrenaline), which interferes with bone building cells and can cause damage to the bones. Therefore, people suffering from depression are prone to osteoporosis.
• Rheumatoid Arthritis/ Ankylosing Spondylitis
Since Rheumatoid Arthritis (RA) and Ankylosing Spondylitis (AS) restrict movement, it generally results in inactivity of the body. Physical inactivity further increases the risk of osteoporosis in people suffering from RA and AS. In these diseases, bone loss occurs more in the areas surrounding the affected joints. The medicines used for the treatment of RA and AS, such as corticosteroids also interfere with bone remodeling. Corticosteroid therapy decreases the production of sex hormone (estrogen) leading to increased bone loss.
• Anticoagulants (blood thinning drugs) such as heparin cause decrease in bone density. These drugs reduce bone mineral content as production of vitamin K (gives strength to the bones) is inhibited by the use of these drugs. These drugs are also linked with increased risk of osteoporotic fractures.
• Proton Pump Inhibitors (drugs used in treatment of peptic ulcers and other digestive disorders) inhibit the production of acidic content in stomach. They interfere with calcium absorption and cause osteoporosis.
• Thiazolidinediones (drugs used to treat diabetes), such as (rosiglitazone, pioglitazone etc) are linked with osteoporotic fractures.
• Aromatase Inhibitors (drug used in breast cancer), such as methotrexate (drug used in arthritis, cancer of skin and lung), depot progesterone and gonadotropin-releasing hormone agonists (used in treating uterine fibroids, endometriosis) causes osteoporosis.
These drugs suppress ovarian activity and causes reduction of estrogen.
• Steroidal Drugs such as glucocorticoids and corticosteroids also cause osteoporosis. These drugs interfere with calcium absorption. Corticosteroid therapy decreases the production of estrogen leading to bone loss.
• Antiepileptic Medicines such as phenytoin, antidepressants (such as barbiturates) and chronic lithium therapy used in bipolar disorders also cause osteoporosis. These medicines accelerate vitamin-D metabolism and block beneficial effects of vitamin-K. These drugs increase cortisol production leading to suppression of sex hormone estrogen.