Developmental changes in the pituitary-gonadal-axis in male Mongolian gerbils from birth to adulthood.

The development of the pituitary-gonadal-axis and of body and organ weights was investigated in male Mongolian gerbils. During the neonatal period from birth to 7 days of age testicular activity was high but decreased to low prepubertal levels from 7 to 28 days of age. The pubertal period occurred from 1 to 3 months of age and was characterized by an intense rise in serum testosterone concentrations and in testicular testosterone production in-vitro. At 2.5 months of age accessory organs achieved their adult weight, at the same time as both, serum testosterone concentration and in-vitro testosterone production, reached their respective maximum levels. From 4 until 24 months of age no further relevant changes occurred in the pituitary-gonadal-axis. This study demonstrates that the testicular responsiveness is an important factor for the pubertal increase of testosterone during sexual maturation of male Mongolian gerbils.