Celiac disease (CD) is an autoimmune disorder where consuming gluten triggers damage to the small intestine, while osteoporosis (OP) is a condition characterized by fragile bones with low mass. CD significantly increases the risk of OP, making bone health a major concern for those with the condition. Estimates suggest that up to 75% of individuals newly diagnosed with CD also have reduced bone mineral density, presenting as osteopenia or osteoporosis. Bone fragility can sometimes be the first noticeable sign of undiagnosed celiac disease. Addressing this risk requires understanding the underlying physiological mechanisms and implementing consistent monitoring and targeted treatment strategies.
The Mechanism of Bone Loss in Celiac Disease
The primary reason celiac disease leads to bone loss is the damage it causes to the lining of the small intestine. When gluten is consumed, the immune system attacks the villi, the finger-like projections responsible for absorbing nutrients. This damage, known as villous atrophy, drastically reduces the surface area available for absorption, leading to malabsorption of several key nutrients.
The malabsorption of calcium and vitamin D is the most direct cause of compromised bone health. Calcium provides bone strength and density, and vitamin D is necessary for the body to absorb calcium efficiently from the gut. Chronic deficiency in these two nutrients prevents proper bone mineralization. Low calcium levels can also trigger secondary hyperparathyroidism, where the parathyroid gland releases excess parathyroid hormone (PTH) to raise blood calcium by actively breaking down bone tissue.
Beyond nutrient malabsorption, the chronic inflammation inherent to celiac disease also disrupts the normal process of bone remodeling. The inflammatory response releases pro-inflammatory cytokines into the bloodstream. These molecules tip the balance of bone turnover in favor of osteoclasts (cells that break down bone) over osteoblasts (cells that form new bone). This accelerated bone resorption, combined with poor mineralization, results in the low bone mineral density characteristic of osteoporosis.
Screening and Monitoring Bone Density
Identifying and tracking bone loss is an important part of managing celiac disease. The standard tool for measuring bone mineral density (BMD) is a Dual-Energy X-ray Absorptiometry (DXA) scan. This scan determines the T-score, which compares the patient’s BMD to that of a healthy young adult. A T-score of -2.5 or lower confirms a diagnosis of osteoporosis.
Guidelines suggest a DXA scan at the time of celiac diagnosis, particularly for adults with malabsorption symptoms or other risk factors for bone disease. For patients with normal BMD, follow-up scans are recommended after two to three years of adhering to a gluten-free diet (GFD). If low bone density is present, a repeat DXA scan may be performed sooner, usually after one year on the GFD, to assess treatment effectiveness.
Blood tests are also used to check for deficiencies that impact bone health, including measuring levels of 25-hydroxyvitamin D and parathyroid hormone (PTH). These tests help identify the severity of malabsorption and guide necessary supplementation. Monitoring these levels is necessary until they return to the normal range, confirming that the intestinal lining is healing and absorption is improving.
Strategies for Restoring Bone Health
The most effective strategy for reversing bone loss in celiac disease is strict adherence to a Gluten-Free Diet (GFD). The GFD allows the damaged villi in the small intestine to heal, restoring the ability to absorb calcium, vitamin D, and other nutrients. This intestinal healing is the foundation upon which all other bone health interventions are built.
Targeted supplementation is crucial, especially in the initial phase after diagnosis. Since most patients have significant deficiencies, high-dose calcium and vitamin D supplements are prescribed to correct malabsorption deficits. While the GFD heals the gut, supplementation ensures the body has the necessary building blocks to remineralize the skeleton. Studies show that BMD improves significantly within the first year on a GFD, with continued gains over the next few years.
For patients with established osteoporosis or high fracture risk, pharmacological treatments may be considered alongside the GFD and supplements. Bisphosphonates, drugs that slow bone breakdown, are used for severe cases, particularly in older adults. However, the effectiveness of oral bisphosphonates can be variable due to impaired absorption in active celiac disease. Therefore, successful adherence to a GFD is a prerequisite for any pharmacological treatment.