Hormone influence on antler growth of white-tailed deer
By Matt Ross, Whitetail Stewards, Inc.
Nearly every hormone and hormone-producing tissue in the deer's body has some influence on antler growth. The effects of these may be direct, indirect or combined. The following describes the step-by-step process in which photoperiod directs these hormones to influence antlerogenesis. The diagram illustrates each step of the process:
• As the length of daylight shortens in the fall and the duration of night is greatest, the light-sensitive portion of the brain (pineal gland) responds by increasing the secretion of the hormone melatonin.
• Rising levels of melatonin cause the pituitary gland to begin production of prolactin and growth hormone.
• The increase in melatonin levels also cause the hypothalamus to pulsate and begin production of gonadotrophin releasing hormone (GnRH).
• Growth hormone from the pituitary triggers the release of insulin-like growth factor (IGF) from the liver and other peripheral tissues. Currently, it is thought that IGF indirectly controls antler growth in the spring and summer.
• GnRH also causes the pituitary to secrete two gonadotrophins, luteinizing hormone (LH) and follicle stimulating hormone (FSH).
• LH stimulates the testicular production and secretion of testosterone, which promotes antler hardening and velvet shedding . Prolactin from the pituitary suppresses testosterone in the late winter, triggering antler shedding .
Summary of Hormone Influence
The following figure shows each stage of antler development in white-tailed deer and the main hormones responsible for controlling each stage.
