Seasonal levels of cortisol, triiodothyronine and thyroxine in male axis deer.

1. Seasonal plasma levels of thyroxine (T4), triiodothyronine (T3) and cortisol were investigated between November and June in seven penned male Axis deer. 2. No distinct seasonal variation of cortisol has been detected. The levels oscillated between 1 and 5 micrograms/dl. 3. The stress of immobilization and sampling had little effect on cortisol levels. Concentrations remained mostly stable in three consecutive samples taken 10 min apart. 4. T3 concentrations were stable between November and March (average values 110-120 ng/dl). After a sharp decline in April (average 70 ng/dl), a strong rebound in May and June was observed. 5. A distinct seasonal peak of T4 (highest individual value, 12.1 micrograms/dl) was detected in March. After a sharp decline in April (lowest individual value, 4.5 micrograms/dl) a strong rebound followed in May.