Growth hormone effects on cortical bone dimensions in young adults with childhood-onset growth hormone deficiency

Abstract

Growth hormone (GH) treatment in young adults with childhood-onset GH deficiency has beneficial effects on bone mass. The present study shows that cortical bone dimensions also benefit from GH treatment, with endosteal expansion and increased cortical thickness leading to improved bone strength.

Introduction: In young adults with childhood-onset growth hormone deficiency (CO GHD), GH treatment after final height is reached has been shown to have beneficial effects on spine and hip bone mineral density. The objective of the study was to evaluate the influence of GH on cortical bone dimensions.

Methods: Patients (n = 160; mean age, 21.2 years; 63% males) with CO GHD were randomised 2:1 to GH or no treatment for 24 months. Cortical bone dimensions were evaluated by digital x-ray radiogrammetry of the metacarpal bones every 6 months.

Results: After 24 months, cortical thickness was increased compared with the controls (6.43%, CI 3.34 to 9.61%; p = 0.0001) and metacarpal index (MCI) (6.14%, CI 3.95 to 8.38%; p < 0.0001), while the endosteal diameter decreased (-4.64%, CI -7.15 to -2.05; p < 0.001). Total bone width did not change significantly (0.68%, CI -1.17 to 2.57%; not significant (NS)). A gender effect was seen on bone width (p < 0.0001), endosteal diameter (p < 0.01) and cortical thickness (p < 0.01), but not with MCI (NS).

Conclusions: Cortical bone reacts promptly to reinstitution of GH beyond the attainment of final height by increasing the cortical thickness through endosteal bone growth. This leads to a higher peak bone mass and may reduce the risk of cortical bone fragility later in life.

Fig. 1

Principles of digital x-ray radiogrammetry. Using a standard x-ray, the region of interest is automatically detected. From the density curve (right), the external and internal diameters are detected (117 lines/cm). The reported bone width (W), cortical thickness (T) and endosteal diameter are the averages of these measurements. Coefficient of variation (CV) 0.65%

Fig. 2

Changes in metacarpal bone dimensions over 24 months (estimated mean ± 95% confidence interval). Solid line growth hormone treatment group, dashed line untreated group. a Bone width (centimetres), b endosteal diameter (centimetres), c cortical thickness (centimetres), d CSMI (×1,000). p values indicate treatment difference from baseline to end of trial. p < 0.0001

Fig. 3

Change in metacarpal index (2CT/W [millimetres per millimetre]) by treatment group and by gender