The annual cycle of antler growth in male mule deer is initiated and controlled by changes in day length acting on cell types that secrete growth-stimulating hormones.
The annual cycle of antler growth in the mule deer is initiated and controlled by changes in day length acting on several cell types of the anterior pituitary. These cell types secrete growth-stimulating hormones that act mainly on the antlers and incidentally on the testes.
Antler hardening, shedding, and even the breeding period are mediated by decreasing day length through the action of gonadotropins on Leydig cells, thus producing androgens. Androgens induce secondary ossification, accelerate maturation, induce behavioral changes that result in shedding antler velvet, and aid in the maintenance of osteoblasts and osteocytes to maintain antlers in hard bone condition. Withdrawal of androgens at the end of the breeding season permits resorption of bone at the pedicel-antler junction and antler shedding.