Comparative Study of the Thyroid Gland of Juvenile Male Guinea Pigs and Grass-cutters: Hematological and Hormonal Profile

This study presents a comparative examination of the hematological parameters, structure, and function of the thyroid gland between two rodent species: guinea pigs (Cavia porcellus) and grasscutters (Thryonomys swinderianus), which are taxonomically distinct. They are important for research and agriculture, yet little is known about their comparative thyroidal morphology, physiology, and hematological profiles. The study utilized six grasscutters and six guinea pigs with an average weight of 1800±530 g and 210±20 g, respectively. The thyroid gland of the guinea pigs is compact, while the grasscutters are bilobed without an isthmus joining the lobes. The average weight of the guinea pigs’ and the grasscutters’ thyroid gland weight was found to be 1.69±0.26 g and 2.81±0.37 g, respectively. The relationship between thyroid hormones (triiodothyronine [T3] and thyroxine [T4]) of the guinea pigs and grasscutters was found to be in line with that of most mammals, with the T4 concentration being significantly higher than the T3 concentration. The differences in the Red Blood cell properties of the guinea pigs and grasscutters were found to be significant at P<0.05, being significantly higher in grasscutters. The differences in the guinea pigs’ and grasscutters’ white blood cell indices were not statistically significant at P<0.05. This study contributes to a deeper understanding of the comparative endocrinology and hematology of guinea pigs and grasscutters, with implications for their use in physiological, toxicological, and pharmacological studies.

Key Words: grasscutters; guinea pigs; hematological parameters; thyroid gland