Longitudinal changes of lumbar bone mineral density (BMD) in patients with GH deficiency after discontinuation of treatment at final height; timing and peak values for lumbar BMD

OBJECTIVE GH treatment has an important role in the acquisition of bone mass in children and adolescents with GH deficiency (GHD). However, there is no information concerning the timing and value of peak bone mass in treated patients with GHD. In adolescents with GHD we longitudinally measured lumbar bone mineral density (BMD) after discontinuation of GH treatment at final height until they achieved lumbar peak BMD (pBMD). Moreover, the changes of lumbar BMD after the attainment of the peak were assessed for a period of 2 years. The results of patients were compared with those obtained in age- and sex-matched healthy controls. PATIENTS AND MEASUREMENTS Lumbar BMDarea [bone mineral content (BMC) corrected by the vertebral surface area scanned] and lumbar BMDvolume (BMC corrected by vertebral volume estimated by a mathematical model), by dual energy X-ray absorptiometry, were assessed in 16 patients (nine males, seven females; aged 14.9-18.8 years) with isolated GHD and 157 healthy subjects (78 males, aged 16.2-24.9 years; 79 females, aged 14.1-22.8 years) as controls. In patients, lumbar BMDarea and lumbar BMDvolume were measured at final height and approximately every year up to 21-24 years and 19-22 years in males and females, respectively; BMD values of the patients were plotted on the reference curves for age and sex obtained in controls. RESULTS At final height, seven male (78%) and five female (71%) patients had a value for lumbar BMDarea below 2SD of normal mean, whereas all patients had a value of lumbar BMDvolume between 0 and -2SD of normal mean. In patients, lumbar pBMDarea and lumbar pBMDvolume were achieved approximately 1-3 years after final height. The timing of lumbar pBMDarea and lumbar pBMDvolume was significantly (P < 0.0001) delayed in patients in comparison with controls (pBMDarea: males, 19.8 +/- 0.6 years and 18.4 +/- 0.6 years; females, 18.0 +/- 0.3 years and 16.7 +/- 0.6 years, respectively; pBMDvolume: males, 19.8 +/- 0.7 years and 18.6 +/- 0.6 years; females, 18.0 +/- 0.4 years and 16.7 +/- 0.6 years, respectively). In addition, mean values for lumbar pBMDarea and lumbar pBMDvolume were significantly (P < 0.01 to P < 0.0001) reduced in patients compared with controls (pBMDarea: males, 1.129 +/- 0.055 g/cm(2) and 1.225 +/- 0.048 g/cm(2); females, 1.122 +/- 0.053 g/cm(2) and 1.227 +/- 0.060 g/cm(2), respectively; pBMDvolume: males, 0.326 +/- 0.010 g/cm(3) and 0.352 +/- 0.036 g/cm(3); females, 0.348 +/- 0.010 g/cm(3) and 0.388 +/- 0.039 g/cm(3), respectively). In patients, mean values of lumbar BMDvolume declined significantly (P < 0.03 to P < 0.01) 2 years after its peak. At any rate, mean values of lumbar BMDarea and lumbar BMDvolume of patients one and two years after their peak remained significantly lower (P < 0.01 to P < 0.0001) than those of controls. CONCLUSIONS The results show that treated adolescents with GHD have an increase of lumbar BMDarea and lumbar BMDvolume after discontinuation of GH treatment at final height, but they have delayed timing and reduced mean values of lumbar pBMDarea and lumbar pBMDvolume in comparison with controls. In patients, mean values of lumbar BMDvolume declined 2 years after its peak. Although the number of the patients was small, the results seem to indicate that GH has a role in the acquisition of lumbar BMD after final height in patients with GHD, suggesting that GH treatment should be continued up to the achievement of lumbar pBMD.