Serum Triiodothyronine, Thyroxine, and Thyroid Stimulating Hormone Concentrations of Domestic Female Cats at Different Reproductive Stages

Abstract

Thyroid hormones have various roles in different physiological systems in the body. Thus, thyroid dysfunction is common in cats, in this study, we aimed to determine the normal values of triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH) in the blood of female cats at different phases of the estrous cycle. Queens were divided into three groups as estrous (n=14), diestrus (n=12), and interestrus (n=10) according to findings of vaginal cytology, ovarian inspection, and serum estradiol (E2) and progesterone (P4) concentrations. Blood samples were collected before the ovariohysterectomy, and the obtained sera were analyzed for free T3, free T4, TSH, E2, and P4. The results showed that the highest T3 and T4 concentrations were found in cats at interestrus while the lowest T3 and T4 concentrations were found at diestrus and estrus, respectively. The level of TSH in all cats was below the detection limit of the assay. The mean concentrations of thyroid-related hormones in each group showed non-significant variations (P>0.05). The correlation between ovarian and thyroidal hormones was not statistically significant (P>0.05). In conclusion, it is required to further comprehensive/experimental studies to exhibit the interaction between ovarium and thyroid gland because of its importance.