Sex steroids have been shown to influence longitudinal bone growth during sexual maturation, partially by increased GH secretion. Mice transgenic for metallothionein promoter bovine GH were developed by pronuclear injection as a model with sex steroid-independent GH secretion. Prepubertal normal and transgenic, male and female mice were either gonadectomized or sham operated. The growth was divided into two segments: peripubertal growth from 30-60 days of age and adult growth from 60-90 days of age. Orchidectomy resulted in a decreased growth rate of the lumbar spine and a decreased weight gain during the peripubertal growth, whereas tibia growth was unaffected. The alteration in proportions between the lumbar spine and the tibia was apparent for both normal and bovine GH transgenic mice, suggesting that the effect was not mediated via decreased GH secretion. Orchidectomy resulted in increased adult tibial growth, whereas weight gain and lumbar growth were unaffected. In female mice, gonadectomy did not influence these parameters during either time period studied. In summary, we present data indicating that the male gonads in a GH secretion-independent manner stimulate pubertal growth of the spine and inhibit the tibial growth of adult animals.