Table. Secondary causes of osteoporosis.

Disorder	Most common fracture site	Primary mechanism
Inflammatory conditions
Rheumatoid arthritis, systemic lupus erythematosus	Hip	High bone turnover due to pro-inflammatory cytokines
Crohn’s disease, ulcerative colitis	Vertebrae	High bone turnover due to pro-inflammatory cytokines, malnutrition and malabsorption
Hypogonadism
Premature menopause (auto-immune, surgical, drugs)	Distal radius (Colles), vertebrae	High bone turnover from low oestrogen or low testosterone
Hypopituitarism (structural or functional)	Distal radius (Colles), vertebrae	High bone turnover from low oestrogen or low testosterone
Endocrinopathies
Hypercortisolaemia (Cushing’s syndrome)	Vertebrae, ribs	Low bone turnover from impaired bone formation and mineralisation
Hyperthyroidism	Hip	High bone turnover from increased bone resorption
Primary hyperparathyroidism	Distal radius, vertebrae	High bone turnover from increased bone resorption
Hyperprolactinaemia	Distal radius, vertebrae	High bone turnover from oestrogen deficiency
Acromegaly	Vertebrae	High bone turnover, increase in bone size and co-existing secondary hypogonadism
Diabetes mellitus	Hip	Low bone turnover from insulinopenia in type 1, mechanism not well understood in type 2
Malabsorption
Pernicious anaemia	Vertebrae	Low bone turnover from impaired osteoblast recruitment
Coeliac disease	Distal radius, vertebrae	High bone turnover due to malnutrition and malabsorption
Gastrectomy	Vertebrae	High bone turnover due to malnutrition and malabsorption
Haematological conditions
Multiple myeloma and monoclonal gammopathy of unknown significance	Vertebrae	Uncoupling in bone turnover (high bone resorption and low bone formation) from pro-inflammatory cytokines
Myeloproliferative disorders	Vertebrae	Direct marrow effects on bone
Systemic mastocytosis	Vertebrae	High bone turnover from mast cell mediators
Abnormal bone architecture
Paget’s disease	Long bones	High bone turnover from overactive bone resorption
Osteopetrosis	Hip, long bones	Low bone turnover due to defective bone resorption
Malignancy (primary or secondary)	Affected bones	High bone turnover from paraneoplastic effects
Other conditions
Chronic liver disease	Vertebrae	Low bone turnover from liver disease and increased bone resorption due to malabsorption, vitamin D deficiency and hypogonadism
Chronic kidney disease	Hip, vertebrae	High bone turnover from osteomalacia, secondary hyperparathyroidism or mixed bone disease, or low bone turnover from adynamic bone disease (from aluminium or iron)
Kidney transplantation	Vertebrae, small bones	High bone turnover and tertiary hyperparathyroidism