Osteometabolic profile and bone mass in the transition phase: ethnic differences in Brazilians treated with somatropin during childhood

Abstract

Objective: The main growth hormone action is to promote linear growth increasing protein synthesis stimulation and osteoblastic activity. Peak bone mass extends from adolescence to 30 years of age. Several factors may influence this acquisition and prevent fracture risk in adulthood, such as genetic potential, GH, ethnicity, and lifestyle factors. This study aims to compare bone mass and osteometabolic profile of white and Afro-descendant Brazilian adolescents in the transition phase, who were treated with human recombinant growth hormone in childhood.

Methods: The authors selected 38 adolescents from the Transition Outpatient Clinic of the University of São Paulo. Lumbar spine and total body bone mineral density (BMD) and bone mineral content (BMC), serum calcium, 25-OH-vitamin D and bone markers were analyzed at the rhGH withdrawal.

Results: The mean age was 16.8 ± 1.6 years. There were 21 Afro-descendant and 17 whites. Thirty-four percent of the sample presented vitamin D insufficiency, 66% inadequate calcium intake and 44.7% physical inactivity. The Afro-descendants showed a lower lumbar spine and total body Z scores than those of the whites (p = 0.04 and p = 0.03, respectively), as well as their mean body weight (p = 0.03). There were no differences in the remaining osteometabolic parameters.

Conclusion: As most adolescents had vitamin D insufficiency, low calcium intake, and physical inactivity, calcium, and cholecalciferol supplementation and lifestyle changes should be encouraged. The Brazilian Afro-descendant may be a vulnerable group for low bone mass, requiring special strategies to increase bone accrual and body weight. More studies are necessary to compare ethnic differences in this population.

Keywords: Bone densitometry; Bone mineral density; GH deficiency; Recombinant human growth hormone; Transition phase; Vitamin D.