The NICE guideline on the recognition, assessment and management of coeliac disease recommends that testing for coeliac disease is considered in anyone with reduced bone mineral density or osteomalacia.
The risk of osteoporosis is higher for those who are diagnosed with coeliac disease late in life due to chronic malabsorption of calcium prior to diagnosis. Treatment is important to avoid complications of osteoporosis such as fractures. There is evidence that early diagnosis and management of coeliac disease in childhood allows normal bone mass to be achieved.
Who is at risk of osteoporosis?
There are many risk factors for osteoporosis including endocrine, metabolic and nutritional disorders, as well as some prescription medication. The list below outlines factors associated with increased risk:
- gender – women have much lower bone density than men
- race – Caucasian and people of Asian origin are at greater risk than people of African American origin
- genetics – a family history of fracture is an important risk factor
- increasing age
- oestrogen levels – after menopause, there is a period of rapid bone loss due to reduced oestrogen. Some women may also lose bone before menopause if they have infrequent periods or lack of normal amounts of oestrogen
- prescription medication – some drugs can affect bone density, such as glucocorticoids, thyroid hormones, heparin, and certain diuretics
- diet – a low calcium diet for many years or chronic malabsorption of calcium is associated with lower bone density
- exercise – lack of bone building exercise, such as walking or running
- smoking – smoking prevents the deposition of bone and is associated with lower bone density in men and women
- alcohol – two or more alcoholic drinks a day have been shown to have the same effect on bone as smoking.
Risk factors related to coeliac disease
Some risk factors, specifically related to coeliac disease, may increase the risk of osteoporosis. These include:
- late or delayed diagnosis of coeliac disease in adult life
- lapses from the gluten free diet
- persistent villous atrophy
- lactose intolerance
- low BMI
How common is osteoporosis in coeliac disease?
There are studies reporting evidence of reduced bone mineral density, in up to 75% of patients at diagnosis. Adhering to a gluten free diet is important to promote healing of the gut lining and to optimise absorption of calcium from the diet. Therefore, strict adherence to a gluten free diet can improve bone mineral density (BMD). The prevalence of reduced bone mineral density after one year of following a gluten free diet is similar to that after three years. This suggests that the extent of bone mass gain in the first year of dietary treatment is indicative of overall BMD improvement.
Causes of loss of bone mass in coeliac disease
The cause of changes in bone health in coeliac disease is multifactorial - both systemic and local mechanisms may play a role.
- Chronic malabsorption – intestinal damage seen in untreated coeliac disease can lead to chronic malabsorption of nutrients including calcium. Calcium malabsorption and subnormal levels of serum calcium result in damage to bone health. Intestinal malabsorption can also result in a reduced BMI. Hypocalcaemia (low serum calcium) can lead to secondary hyperparathyroidism. Hyperparathyroidism leads to high levels of parathyroid hormone which results in further loss of calcium from the bones.
- Reduced calcium intake – some people with coeliac disease reduce their intake of calcium rich dairy foods eg milk and milk products due to secondary lactose intolerance. Dietary advice to replace calcium rich foods is essential in this situation.
- Bone formation – osteoblasts play a role in the formation of bone. Osteoclasts are cells which are responsible for the removal of bone. The balance of osteoblasts and osteoclasts is important for bone repair. Pro-inflammatory cytokines are responsible for osteoclast activation. Cytokines can have an impact on both normal and abnormal bone formation. In coeliac disease increased resorption (where old bone is removed from the skeleton) is not balanced out by increased bone formation. These changes in bone are similar to those seen in Crohn's disease.
- Gynaecological disorders – in women with coeliac disease, the role of associated gynaecological disorders should be considered. Amenorrhoea is a more common finding in coeliac disease than the general population and sex hormone imbalance represents an important risk factor for the development of osteoporosis.
Diagnosing low bone mineral density
Diagnosis of osteoporosis in people with coeliac disease is determined by a Dual energy X-ray absorptiometry (DEXA) scan which measures bone density. The World Health Organisation (WHO) recommends using measurements from a T-score for determining bone mass.
The T-score is an index representing the number of standard deviations by which the patient value differs from the average peak bone mass of a young adult reference population. A diagnosis of osteopenia is made when the T-score is between -1 and -2.5. A diagnosis of osteoporosis is made when the T-score is less than -2.5.
DEXA scan follow up and calcium supplementation
The need for a DEXA scan and calcium supplementation should be assessed on an individual basis as part of the annual review. NICE guideline for coeliac disease (2015) recommends the need for a dual-energy X-ray absorptiometry (DEXA) scan should be assessed in line with the NICE guideline on osteoporosis: assessing the risk of fragility fracture or active treatment of bone disease.