Endocrine Abstracts

Objective: The pathophysiology of the increased fracture risk in Type 1 Diabetes (T1D) remains unclear. Given that childhood and adolescence are important physiological periods for optimal bone development, we performed a multimodality assessment to determine the effects of T1D on bone health.

Methods: Thirty two affected children at a median (range) age of 13.7 years (10.4, 16.7), were recruited for detailed assessment of bone health. Serum bone alkaline phosphatase (BAP) and c-terminal telopeptide of type 1 collagen (CTX) as well as DXA total body (TB) and lumbar spine (LS) bone mineral content (BMC) adjusted for bone area were converted to SDS. 3T MRI was performed to assess proximal tibia bone microarchitecure and vertebral marrow fat fraction (%) and compared to 26 healthy controls.

Results: In T1D, BAP SDS and CTX SDS were −0.6 (−2.5,+2.1) and −1.1 (−2.5, +0.5) and TB and LS BMC SDS were −0.1 (−1.1, 0.9) and −0.3 (−1.0, 1.8), respectively. Trabecular volume (appBV/TV) and trabecular number (appTbN) were lower in cases with corresponding higher trabecular separation (appTbSp) compared to controls at 0.55 (0.47, 0.63) vs 0.59 (0.47, 0.63) (P=0.024), 1.67 (1.56, 1.93) vs 1.82 (1.56, 1.99) (P=0.004) and 0.27 (0.21,0.32) vs 0.24 (0.20,0.33) (P=0.001), respectively. The marrow fat fraction in cases and controls was similar at 23% (11, 66) and 20% (8, 61), respectively (P=0.25). T1D cases with poor glycemic control HbA1c>75 mmol/mol had lower BAP SDS compared to those with good control HbA1c<58mmol/mol (P=0.009). BAP SDS were also lower in children with acidosis at initial presentation (P=0.017) and higher in children on continuous subcutaneous insulin infusion (P=0.025). Fractures were encountered in 10/32 (31%) cases after diagnosis of T1D and 5/26 (19%) controls (P<0.001). T1D children who fractured had poorer glycaemic control (P=0.007) and lower TB BMC SDS (P<0.001). There was no significant difference in bone microarchitecture or marrow adiposity between the fracture groups.

Conclusion: Children with T1D display a low bone turnover state with reduced bone mineralisation and poorer bone microarchitecture. Bone formation was affected by glycemic control, acidosis at T1D presentation and insulin delivery whilst fractures were associated with bone mineral status.