Fracture risk is decreased in acromegaly--a potential beneficial effect of growth hormone.

Growth hormone (GH) is an anabolic hormone that may increase bone density and thus decrease fracture risk. Patients with acromegaly have an excess of GH, and we therefore investigated whether fracture risk was decreased in patients with acromegaly. We identified 206 patients newly diagnosed with acromegaly between 1983 and 1996 who underwent pituitary surgery. Each patient was compared with three age- and gender-matched controls randomly selected from the background population. Mean age at diagnosis was 46.0+/-12.6 years and 50% were women. Before diagnosis, six patients sustained six fractures during 2128 person years and after diagnosis six patients had ten fractures during 1282 years of follow-up. Among the controls, the corresponding figures were 23 subjects with 44 fractures during 6357 years of follow-up before diagnosis and 46 fractures in 28 subjects during 4051 person years. The fracture rate was significantly decreased before (incidence rate ratio: IRR=0.41, 95% CI: 0.18-0.93) but not after the diagnosis (IRR=0.69, 95% CI: 0.35-1.36) of acromegaly was made. Twenty-three patients had undergone measurements of bone mineral density by DXA after diagnosis, and their mean+/-SD Z-scores both in the lumbar spine (0.92+/-1.38) and femoral neck (0.54+/-1.02) were significantly higher than expected. A fracture before diagnosis was a significant risk factor for sustaining an incident fracture after diagnosis (RR=11.8, 95% CI: 4.7-29.3). In conclusion, fracture risk is significantly decreased in patients with acromegaly compared to controls probably due to an anabolic effect of growth hormone on bone.