Effects of delaying puberty on bone mineralization in female rats

The effect of delaying puberty on bone mineralization was studied using fem ale rats as a model. Repeated injections of gonadotrophin-releasing hormone antagonist (GnRHa) were used to suppress the onset of puberty from the age of 6-10 weeks. A group of control female rats was given aqueous solution i njections at the same age and for the same duration. The effect of delaying puberty on bone mineralization was examined using dual energy X-ray absorp tiometry (DXA) and peripheral quantitative computerized tomography (QCT), b oth methods being adapted for small animals. Bone mineral parameters were m easured at baseline and at the ages of 10, 17 and 24 weeks in total body, f emur and spine. Compared to controls, bone mineral content (BMC) and bone m ineral density (BRID), as measured by DXA, were significantly decreased in GnRHa-treated rats in total body and femur at 10 and 24 weeks of age (P < 0 .05). The results were even more significant after adjusting for weight. af ter this adjustment, spine BMC and BMD at 10, 17 and 24 weeks were signific antly lower in the treatment group (P < 0.05). Trabecular BMD at the distal femur in the GnRHa treated group as measured by peripheral QCT was signifi cantly lower (P < 0.05). However, cortical bone in the mid-femur had higher BMD, concurrent with lower cortical thickness in the treatment group. In c onclusion, a delay in the onset of sexual maturation may cause prolonged, p ossibly irreversible defect in bone mineralization.