I had been curious to understand more about the shedding of antlers. Had asked my naturalist and also looked into it more. Here is a broad level understanding.
Antlers are bones composed of calcium and phosphorus which are grown and shed each year. The antlers grow onward from the skull through attachment points which are known as 'pedicles'. These pedicles are formed a couple of months from birth and provide the base for the antlers to grow. Velvet covers a growing antler, which supplies oxygen and nutrients to the growing bone. Once the antler achieves its full size, the velvet is lost and the antler's bone dies. These are the antlers at the mature stage, as seen in the picture. This coincides with increasing testosterone levels during rutting season. Once the rutting season is over, in response to decreasing testosterone, 'osteoclasts' erode the base of the antlers at their junction with the pedicle, eventually causing the antlers to simply fall off. Each year a larger and more branched set of antlers will develop. The entire process of growth and regrowth of antlers is quite demanding in terms of nutrition and hence is considered to be an indicator of good health.
Hope that helps.. do look into it more if interested and add if i missed anything!