Causes of osteoporosis & osteopenia

Causes of osteoporosis & osteopenia

There are many causes of osteoporosis. Not only do bones lose density with age, medications used to treat breast cancer, arthritis, asthma, Crohn's disease and Addison's disease can also lower bone density. Some illnesses such as hyperthyroidism, hypopituaritism and eating disorders also cause bones to lose strength. You will find information on all of these causes of lowered bone density, along with the role of oestrogen in bone density.

Osteoporosis is a condition in which bones become thinner, or lose 'bone mineral density'. This leads to an increased risk for fractures. Osteoporosis is more common in women, especially after menopause. However, a number of conditions may be associated with a decrease in bone density.

The things that affect bone density include:

Ageing

Ageing reduces bone strength because more bone is broken down than can be made – everyone develops osteoporosis if they live long enough.

Alcohol

Excessive alcohol intake increases the risk of developing osteoporosis.

Breast cancer

Women with breast cancer have an increased risk of developing osteoporosis because of the treatments used and their effect on oestrogen levels.

Calcium

A lack of calcium affects bone strength and the muscles that support bones, so adequate intake is essential.

Corticosteroid therapy

A steroid replacement hormone including:

• Prednisolone
• Cortisone
• Hydrocortisone
• Dexamethasone
  

Long-term use (more than 2 months) of oral corticosteroid type medications, with doses of more than 5-7.5mg of prednisolone per day, increases the risk of developing osteoporosis[1] by reducing bone formation and bone density

If other risk factors for osteoporosis (such as being postmenopausal) are present, the effect on bones will be more severe

Corticosteroid therapy may be prescribed for a variety of conditions such as:

• chronic airways disease
• asthma
• rheumatoid arthritis
• inflammatory bowel diseases (i.e. Crohn's disease)
• certain skin conditions
• inflammatory conditions such as polymyalgia rheumatic (affects muscles and joints causing pain and stiffness)
• Addison's disease: This causes a deficiency in the hormone cortisol and is treated with corticosteroid drugs to replace the cortisol

Eating disorders (including anorexia nervosa and bulimia)

• Eating disorders cause a loss of bone density because they create deficiencies in nutrition, which in turn affects hormone levels
• If you stop having your periods (due to poor nutrition and/or excessive exercise routines) this reduces your oestrogen level, which reduces your bone density

Eating disorders in early adolescence, when the skeleton is in the process of growing, severely reduce the potential to achieve peak bone mass and this can lead to osteoporosis in women as young as the early 20s. If you develop an eating disorder after the process of skeletal growth has been completed you still risk reducing your bone mineral density.

Excessive exercise

• Although exercise is vital for the development of peak bone mass in childhood and adolescence, excessive or elite level exercise in the adolescent years may have negative effects on your ability to achieve peak bone mass
• Athletes who have periods tend to have normal or increased bone density, whereas athletes who do not menstruate have reduced bone density[2]
• Some activities can help maintain or increase bone mass

Family history

You are at increased risk of osteoporosis if you have a family member with osteoporosis, especially a parent or sibling who has had a hip fracture.

Hormones

A drop in oestrogen can cause a loss in bone strength and this means bone density may be decreased:

• if you have late onset of menstrual periods
• absent or infrequent menstrual periods
• by premature or early menopause
• with menopause

Hyperthyroidism (overactive thyroid)

• High concentrations of thyroid hormone can lead to more bone breakdown than bone formation, which affects bone density and causes osteoporosis
• Graves' disease can result in an overactive thyroid
• If the thyroid condition is treated with a thyroxine hormone (sold as Oroxine and Eutroxsig), there has been concern that an over replacement may also impact on bone health

Hypopituitarism (pituitary gland failure)

• Hypopituitarism can cause a deficiency in cortisol and the usual treatment is long-term replacement of the cortisol with corticosteroid drugs
• There is increasing evidence the doses of corticosteroid drugs to replace the cortisol can lead to osteoporosis – usually this is when the dosage is too high or when there are other co-existing risk factors for osteoporosis

Illness/diseases

Illness or diseases, and sometimes their treatments, can affect bone strength including:

• chronic liver disease
• chronic kidney disease
• Coeliac disease

Physical inactivity

Lack of physical activity reduces bone and muscle strength, which increases the risk of fractures and falls.

Rheumatoid arthritis

Rheumatoid arthritis is an inflammatory disorder that may affect tissues and organs, but principally attacks flexible joints (i.e. elbows and knees). It is a condition affecting approximately 1% of the population, with women affected around 3 times more than men.

If prednisolone is prescribed as part of the medical treatment, this can also lead to the development of osteoporosis, especially in bones adjacent to the affected joints.

Smoking

Smoking, especially how much you smoke, can cause:

• a significant reduction in bone density leading to an increased risk of fracture
• you to experience menopause 1.5-2 years earlier, so you risk developing osteoporosis earlier than average

Vitamin D

Low vitamin D can reduce the body's ability to absorb the calcium required for bone strength.

Lack of oestrogen & bone health

The sex hormone oestrogen plays a vital role in the development of bones.

Adolescence - 20's

• During puberty (10-17 years) sex hormones increase rapidly and these increased levels of oestrogen and testosterone lead to increased bone mass
• The ongoing production of oestrogen is vital in adolescent females and young women to develop and maintain bone mass

30's - 40's

• The balance between bone loss and bone formation changes around 30 years of age and you start to lose more bone than you make
• In the years immediately before menopause there can be a drop in oestrogen levels and this can lead to a reduction in bone mineral density[3]

Menopause

• Menopause means a dramatic fall in oestrogen levels and the loss of bone is accelerated
• This period of significant bone loss can last from 4-8 years after the onset of menopause
  • Bone loss is most severe during the first 3 years after menopause when you may lose approximately 2% of bone mass per year in your spine, hip or wrist
  • The rate of bone loss then slows and you may lose less than 1% of bone density at the hip per year and less in the spine[4]

** Currently under review **

This web page is designed to be informative and educational. It is not intended to provide specific medical advice or replace advice from your health practitioner. The information above is based on current medical knowledge, evidence and practice as at December 2013.