Severe Osteoporosis in a Young Woman With Type 1 Diabetes and Pancreatic Exocrine Insufficiency

Patients with type 1 diabetes mellitus (T1DM) are at increased risk of osteoporosis; however, contributing secondary factors may be under-recognised. We report a case of a 29-year-old woman with a 10-year history of suboptimally controlled T1DM (HbA1c 10.1%-14.7%) who presented with an atraumatic tibial fracture and vertebral compression fractures. She had a history of significant weight loss (nadir 37 kg) and chronic malabsorption. Investigations demonstrated severe pancreatic exocrine insufficiency (PEI; faecal elastase 42 μg/g), vitamin D deficiency (25 nmol/L), and secondary hyperparathyroidism (PTH 10.8 pmol/L). Dual-energy X-ray absorptiometry revealed reduced bone mineral density at the total hip (Z-score -3.4) and lumbar spine (Z-score -2.1). Management included pancreatic enzyme replacement, vitamin D and calcium repletion, and optimisation of glycaemic control. At the 12-month follow-up, biochemical parameters improved (vitamin D 112 nmol/L), and no further fractures occurred. This case highlights the importance of identifying secondary contributors to bone fragility in young patients with T1DM, particularly malabsorption due to PEI.