THE EFFECTS OF ANDROGENS ON THE MECHANICAL-PROPERTIES OF PRIMATE BONE

Feral adult female cynomolgus monkeys were divided into three groups a nd treated for two years: (1) normal controls; (2) weak androgenic tre atment (androstenedione + estrone); and (3) strong androgenic treatmen t (testosterone). The tibiae and the trabecular bone of femoral head f rom each group were tested mechanically. There were no significant cha nges in the elastic modulus and shear modulus of the tibiae, measured by three point bending and torsion tests, among the three groups. Sign ificant increases in energy absorption capacity (+45% for testosterone ) and maximum shear stress (+19.4% for androstenedione and +39% for te stosterone) of the tibiae, measured by torsion tests, and the cortical bone density (+5;5% for androstenedione and +8.7% for testosterone), were observed. Testosterone treatment significantly increased torsiona l rigidity (+23%) and bending stiffness (+15%) of the tibiae while and rostenedione did not change any of these structural properties. The re sults of compression tests of the trabecular bone samples indicated si gnificant increases in their elastic modulus after androstenedione (+8 8%) or testosterone (+107%) treatment. The maximum compressive stress of the testosterone treated samples was significantly higher than thos e of both normal (+28%) and androstenedione treated groups (+26%). The trabecular bone density increased after both androgenic treatments. T his increase was significant for the testosterone treated group (+8.6% ). We conclude that in the young cynomolgus monkey, long-term androgen ic treatment significantly improves some of the mechanical properties of both cortical and trabecular bones, increases bone density, and the stronger the androgen, likely, the more pronounced is the effect.