Orchidectomized (orx) marmoset (Callithrix jacchus) as a model to study the development of osteopenia/osteoporosis.

The common marmoset serves as a primate model for many human diseases. Hypogonadal and particularly aged men develop osteopenia or osteoporosis. Whether marmosets develop osteoporosis after orchidectomy is not known. This was tested in seven young and two older adult male orchidectomy animals using quantitative computer tomography, which allowed quantification of total surface and density of the cortex and of the cancellous structures of the metaphysis of the tibia and of the fifth or sixth lumbal vertebra (L5/L6) before or after orchidectomy (orx), and 1, 6 and 12 months later. Surrogate parameters of whole skeletal bone metabolism (osteocalcin, OC) and C-terminal breakdown products (telopeptides) of collagen-alpha1 (CrossLaps) were also measured. Male marmosets lost between 5 and 20% of their initial cancellous density in the metaphysis of the tibia and this was statistically significant 6 months after castration. No loss of cancellous density was observed in L5/L6 of young marmosets and OC and the CrossLaps in the serum were decreased at this time point while a reduction was observed in bone mineral density of L5/L6 in two aged animals. It is concluded that castration of young male marmoset for 1 year results in a significant loss of bone mineral density in the metaphysis of the tibia resulting in osteopenia but not in the vertebra. The results indicate that male orx marmosets become osteopenic within 12 months after castration and may be a more human-like experimental model for bone research.