Developing antler, a model for endocrine regulation of bone growth. Concentration gradient of T3, T4, and alkaline phosphatase in the antler, jugular, and the saphenous veins.

Thyroxine (T4), triiodothyronine (T3), and alkaline phosphatase (AP) were assayed monthly in white-tailed deer plasma obtained from the antler (A), jugular (J), and the saphenous (S) veins during the period of antler growth and the period of mineralization. The concentrations of T3, T4, and AP in the J and S were not significantly different in any month. During the most intense antler growth period (June and July) AP levels were significantly higher and T3 significantly lower in A as compared to J and S, but no differences were found during the mineralization phase in August. T3 values from all three veins were significantly lower in the mineralization period than J and S values during the growing phase. Variations of T4 levels between A, J, and S as well as differences between months were only negligible. The data indicate that AP is produced in large quantity in the antler tissue during the growth period, but the amount is sharply reduced during the mineralization phase. T3 is utilized in the growing antler; the rate of utilization correlates with the intensity of antler growth. T4 is probably not utilized in the antler bone. Developing antler might be used as a model to study growth and mineralization processes of bony tissues.