The role of androstenedione and testosterone in the reproduction and antler growth of a male white-tailed deer.

Seasonal levels of androstenedione and testosterone were investigated in plasma of mature intact and castrated male white-tailed deer. In four intact bucks, androstenedione concentrations were low in February and March (around 1 nmol/l) and then increased significantly (P less than 0.05) from April to November (peak 2.34 nmol/l). Testosterone remained low (below 3.5 nmol/l) from February to August and then rose significantly (P less than 0.01) till November (peak 36.78 nmol/l). Both hormones declined from November to February. In three castrates, androstenedione levels remained virtually unchanged (averaging around 0.5 nmol/l) between January and September. After a rapid significant increase (P less than 0.05) till November (peak value 2.45 nmol/l), androstenedione concentrations declined quickly to a baseline level. Testosterone in castrates remained around 0.3 to 0.7 nmol/l for most of the year with a non-significant peak (1.45 nmol/l) in October. These data indicate that the spring and summer increase in androstenedione in the intact deer is of testicular origin; the fall peak, however, may be a result of increased production in the adrenal glands. It can be speculated that the increase in androstenedione in the blood of the male deer during the spring may be responsible for the seasonal initiation and support of antler growth as well as being supportive to the re-activation of the reproductive system.