• hexavalent chromium;
  • acute exposure;
  • pituitary–thyroid axis;
  • histopathology;
  • immunocytochemistry;
  • hormone assay;
  • Channa punctatus


Acute exposure to hexavalent chromium (10 mg L−1, 20 mg L−1, and 40 mg L−1 potassium dichromate for 96 h) dose-dependently affected the pituitary–thyroid axis of teleost, Channa punctatus. Significant hypertrophy of the thyroid follicle was observed in 20 mg L−1 and 40 mg L−1 groups; the follicular epithelium was however hypertrophied only in 40 mg L−1 group. The colloid depletion in the lumen of thyroid follicle was evident in 20 mg L−1 and 40 mg L−1 groups. Serum thyroid hormones (thyroxine/T4 and triiodothyronine/T3) level increased significantly at both the higher doses. Increased immunointensity and significant hypertrophy of the pituitary thyrotrophs (anti TSHβ-immunoreactive cells) was observed in both 20 mg L−1 and 40 mg L−1 chromium-exposed fish. The increased thyroid hormones secretion observed in this study might be an adaptive response of the pituitary–thyroid axis under acute chromium-induced stress condition to maintain homeostasis. The long-term Cr(VI) exposures, however, may lead to attenuation/exhaustion of the pituitary–thyroid axis and pose serious threat to fish health and affect their population. © 2013 Wiley Periodicals, Inc. Environ Toxicol 30: 621–627, 2015.