A study was conducted to study the hormonal dynamics in a chicken population divergently selected for phytate phosphorus bioavailability (PBA) in chickens. The utilization of phytate phosphorus in poultry is an important issue because excessive loss of phosphorus (P) in the excreta leads to environmental pollution. From the hormonal dynamics study, it was established that insulin like growth factor I (IGF I) and T3 (triidothyronine) were higher in the high PBA line compared to low PBA line. On the other hand, glucagons levels were higher in low PBA line compared to high PBA line. Leptin levels were not different in the two lines. Increased levels of IGF I and T3 may be responsible for the increase PBA in the high line. On the other hand high glucagon levels in the low line may have negative effect on both calcium and phosphorus bioavailability. Both IGF-I and glucagon were moderately heritable in both high and low PBA lines, whereas T3 was heritable only in the high line. This study provides us some insight into the physiological state of chicken when selected for high and low phytate phosphorus bioavailability.