Osteoporosis Complete Overview

What is Osteoporosis?

Osteoporosis is a bone disease caused when bone mineral density and bone mass decreases and the structure and strength of bone changes. The strength of bones decreases as a result which ultimately increases the risk of fractures.

Osteoporosis is asymptomatic. Hence, it is a “silent” disease. You don't even know that you are suffering from the condition until a fracture happens. It is one of the major causes of fracture in older women and post-menopausal women. Fractures mostly occur in the following bones:

• Hip
• Vertebrae
• Wrist

What are the Causes of Osteoporosis?

Changes in hormone levels can increase the chance of developing osteoporosis.

• Low estrogen levels postmenopausal can lead to osteoporosis
• Low estrogen levels as a result of abnormal periods in premenopausal women.
• Low level of testosterone in men. But, the decrease in the level of testosterone with increasing age will not lead to osteoporosis.

Diet

• Vitamin D and Calcium deficient diets throughout life, starting from childhood can increase the risk of developing osteoporosis.
• Poor protein intake can also be a potential cause.

Certain Medical Conditions

• Endocrine and hormonal diseases.
• Gastrointestinal diseases
• Rheumatoid arthritis
• Certain types of cancer
• HIV/AIDS
• Anorexia nervosa

Long-term use of the following medications can increase the risk of osteoporosis

• Glucocorticoids and adrenocorticotropic hormone (Taken in order to treat asthma and rheumatoid arthritis).
• Proton pump inhibitors (Taken to lower acidity).
• Antiepileptic medicines (taken to treat seizures and other neurological conditions).

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Epidemiology of Osteoporosis

• 200 million people are believed to have osteoporosis according to some recent studies.
• It is a condition that is found to be more prevalent among women than in men.
• This is the lower bone mass density in women which increases with increasing age also.
• In the developed countries: 2 to 8%: Males are affected and 9 to 38% females are affected
• The frequency of fractures is most common among postmenopausal women when compared to that of older women.
• Globally speaking:

 1 in 3 women have an osteoporotic fracture.

 1 in 5 men have an osteoporotic fracture.

• White and Asian people are at greater risk when compared to that of Africans when taking ethnicity into concern.
• People living in areas of higher latitude (e.g., Northern Europe), receive lesser Vitamin D. Hence, are at higher risk of the condition.
• Whereas people living next to the equatorial region are at lesser risk of vitamin D deficiency and hence are at lesser risk of osteoporosis.

Pathophysiology of Osteoporosis

• Osteoporosis is a perfect example for a multifunctional disease.
• A complex interplay of the following factors contributes to a\ person's risk of developing the disease:
  • Genetic factors
  • Intrinsic factors
  • Exogenous factors
  • Lifestyle factors
• In a normal bone, constant growth of bone mass and thus bone remodeling takes place.
• Three main mechanisms that can lead to osteoporosis are the following:
  •  Inadequate peak bone mass (The skeleton develops insufficient mass and strength during growth)
  • Increased bone resorption which can lead to bone loss
  • Inadequate new bone formation during bone remodeling.
• These processes take place in the bone multicellular units (BMUs). They are:
  • Osteoclasts
  • Osteoblasts
• Loss of bone mass occurs through the activation of the osteoclastogenic pathway.
• Two main cells are involved in this particular pathway which plays a significant role in the pathogenesis of osteoporosis. They are osteoclasts and osteoblasts.
  • Osteoblasts: Responsible for bone resorption.
  • Osteoclasts: Determine the final outcome of bone resorption.
• The balance of these two activities is essential and it is influenced by macrophages and innate adaptive immunity.
• This ultimately helps in the formation of a normal bone.
• Bone mass loss which can lead to osteoporosis happens when the balance between the osteoclastic and osteoblastic activity is disrupted.

Role of Hormones

• Estrogen and calcium in addition to that also plays a major role in bone turnover.
• Bone mass formation or bone deposition will be impaired due to vitamin D deficiency and calcium deficiency.
• This leads to secretion of parathyroid hormones (Parathormone and PTH) by the parathyroid gland.
• This is to ensure adequate calcium level in the blood and thereby increasing bone resorption.

Genetics

• Certain genes are involved in the pathogenesis of osteoporosis.
• Mutation caused in these genes can lead to certain rare diseases:
  • Osteoblast regulatory gene
  • Osteoclast regulatory gene
  • Bone matrix elements gene
  • Hormone/receptor genes

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Diagnosis 

Clinical Features

Osteoporosis is generally asymptomatic. Hence, sometimes it is also called silent disease. The following signs should be taken into concern whatsoever:

• Change in posture: Stooping or bending forward
• Loss of height: Getting shorter by an inch or more than an inch
• Bone fractures
• Shortness of breath: Which is caused due to decreased lung capacity which is a result of disc compression.
• Pain in the lower back

Investigations

Routine Screening

Routine screening is advised for individuals especially at risk of developing osteoporosis like:

1. Women over an age of 65

2. Women of any age who have an increased chance of developing osteoporosis.

Physical Examination Which Includes Checking Of:

• Change in body posture
• Balance and gait (the way the individual walks) is checked
• Loss of height and weight
• Muscle strength (Checking the patient's ability to stand from a sitting position without using arms for support)

Testing Bone Mineral Density (BMD):

BMD is usually tested at specific bone areas like in the spine or hip. It can be used to understand the following factors:

1. Diagnose osteoporosis
2. Detecting low bone density before the development of osteoporosis
3. To monitor the efficiency and effectiveness of the current treatment followed by the Patient.
4. For predicting the risk of any future fractures

• The most common test for measuring BMD is dual energy-Xray-absorptiometry (DXA). It is a quick, noninvasive and rather painless test. BMD measurement using DXA is considered as the most reliable way to diagnose osteoporosis and predict any future fractures that are common among patients with osteoporosis.

Conventional Radiography

• The main radiographic features of generalized osteoporosis are the following:

1. Cortical thinning

2. Increased radiolucency

• One of the most frequent complications of osteoporosis is spinal fracture.
• This can be diagnosed and also follow-up can be done to a huge extent with the help of spinal radiography.
• Vertebral height can be measured by using plain-film- X-rays.
• Conventional radiography (CT and MRI) can be helpful in diagnosing and detecting the complications of osteopenia (Reduced bone mass before development of osteoporosis). Radiography cannot detect the early onset of bone loss.
• It can only be of any use if a considerable amount of bone loss has taken place.

How to manage Osteoporosis?

The treatment of osteoporosis aims to slow down or cease the bone degradation and to prevent fractures. Management options include:

• Proper nutrition
• Exercise
• Lifestyle changes
• Prevention of fractures rench pathologist Jean Lobstein coined the term “osteoporosis”.

Nutrition

Following a balanced diet.

• Calcium and vitamin D rich diets are to be followed as they are important in preventing osteoporosis and helps to achieve peak bone mass.
• Good calcium sources are:
  • Green leafy vegetables
  • Broccoli
  • Low-fat dairy products
  • Sardines and salmon with bones
  • Calcium fortified food:
• Tofu
• Soymilk
• Orange juice
• Breads
• Cereals
• Calcium absorption from the intestine is facilitated by vitamin D.
• Sources of vitamin D include:
  • Sunlight
  • Fatty fish
  • Fish oils
  • Egg yolks
  • Liver

Lifestyle

• Staying clear of smoking and intense alcohol intake.
• Regular checkups.

Exercise

• It is an important factor of osteoporosis treatment.
• Regular exercise can help older adults to build muscle mass and strength and to improve coordination and balance.

Medications

The following factors determines the kind of medication to be prescribed to an individual:

• Age
• Sex
• General health
• Amount of bone lost

Medications usually prescribed for osteoporosis include:

• Bisphosphonates: Preserve bone density and strength.
• Calcitonin: Approved for postmenopausal women who cannot take other medications.
• Estrogen agonist/antagonist: Is also known as selective estrogen receptor modulator (SERM) and tissue selective estrogen complex (TSEC). Helps to improve bone density and decrease bone fractures.
• Parathyroid hormone (PTH) analog and parathyroid hormone related-protein (PTHrP) analog:
• Increases bone mass in postmenopausal women and men with osteoporosis.
• Estrogen and hormone therapy: Estrogen and combined estrogen and progestin therapy helps to prevent osteoporosis and fractures in postmenopausal women.
• RANK ligand (RANKL) inhibitor: helps to slow down bone loss in postmenopausal women, men who have bone loss, women who have bone loss and are being treated for breast cancer and men and women who do not respond to any other form of medications.

Points to remember

• French pathologist Jean Lobstein coined the term “osteoporosis”.
• Hip fractures are responsible for the most serious consequences of osteoporosis.
• As human bone is porous in nature, the frequency of severe osteoporosis and related fractures is higher.
• Chemical biomarkers are helpful in detecting bone degradation or loss.
• An enzyme called cathepsin K breaks down an important constituent of the bone called type-I-collagen. The resulting fragment is known as neoepitope. This can be detected by prepared antibodies. This is considered as a method to diagnose osteoporosis.

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