Abstract
Background:
Chronic stress affects endocrine, biochemical, hematological, and behavioral functions, thereby influencing metabolic regulation, immune responses, and neurological activity.

Aim:
This study aimed to investigate the effects of chronic noise stress on hormonal, biochemical, hematological, and behavioral parameters in Wistar albino rats, with particular emphasis on sex-specific differences.

Methods:
Twenty Wistar albino rats (control: n = 10; noise-stress: n = 10) were distributed equally by sex and maintained under standard laboratory conditions. The noise-stress group was exposed to white noise (70 dB) for 1 h daily for 30 consecutive days, whereas the control group was maintained in a quiet environment. T4 and total cholesterol concentrations were measured in lithium-heparinized whole blood samples using a veterinary biochemistry analyzer, and hematological parameters were assessed using an automated hematology analyzer. Behavioral parameters were evaluated based on activity levels and stress-related observations. Statistical analyses were performed using the independent-samples t-test, with a P value < 0.05 considered statistically significant.

Results:
T4 concentrations were significantly higher in the noise-stress group than in the control group (P < 0.001). T4 was also higher in the noise-stress group in male rats (P = 0.025). The total cholesterol concentrations were significantly lower following noise exposure in both female (P < 0.001) and male rats (P = 0.007). Hematological analysis revealed higher WBC, granulocyte, and MID cell counts and lower lymphocyte percentages in female rats. Lymphocyte percentage tended to decrease in male rats, whereas platelet-related parameters showed descriptive increases following noise exposure. Behavioral observations indicated increased stress-related responses, including increased aggression, heightened responsiveness to external stimuli, altered locomotor activity, and increased food and water intake, in the noise-exposed group compared with the control group.

Conclusion:
Chronic noise stress induced significant hormonal, biochemical, hematological, and behavioral alterations. Female and male rats displayed different patterns of metabolic, immune, and behavioral responses to noise stress.

Key words: Behavioral response; Cholesterol; Hematological parameters; Noise stress; Thyroxine.