The effect of biochemical remission on bone metabolism in Cushing's syndrome: a two-year follow-up study

Abstract

Endogenous Cushing's syndrome (CS) is a rare cause of secondary osteoporosis. The long-term consequences for bone metabolism following successful surgical treatment remain largely unknown. We assessed bone mineral density and fracture rates in 89 patients with confirmed Cushing's syndrome at the time of diagnosis and two years after successful tumor resection. We determined five bone turnover markers at the time of diagnosis, one and two years postoperatively. The bone turnover markers osteocalcin, intact procollagen-IN-propeptide (PINP), alkaline bone phosphatase, CTX-I, and TrAcP 5b were measured in plasma or serum by chemiluminescent immunoassays. For comparison, 71 sex-, age- and BMI-matched patients in whom Cushing's syndrome had been excluded were studied. None of the patients received specific osteoanabolic treatment. At time of diagnosis, 69% of the patients had low bone mass (mean T score = -1.4±1.1). Two years after successful surgery, the T score had improved in 78% of patients (mean T score 2 years postoperatively -1.0±0.9). The bone formation markers osteocalcin and intact PINP were significantly decreased at time of diagnosis (p ≤ 0.001 and p = 0.03 respectively), and the bone resorption marker CTX-I and TrAcP 5b increased. Postoperatively, the bone formation markers showed a 3 to 4-fold increase one year postoperatively, with a moderate decline thereafter. The bone resorption markers showed a similar but less pronounced course. This study shows that the phase immediately following surgical remission from endogenous CS is characterized by a high rate of bone turnover resulting in a striking net increase in bone mineral density in the majority of patients. This article is protected by copyright. All rights reserved.