Biochemical and histological evidence of thyroid gland dysfunction in estradiol valerate model of the polycystic ovary in Wistar rats

Abstract

Thyroid defects and polycystic ovary (PSO) disease are prevalent endocrine problems among humans. While various studies investigated the ovarian function and histological alterations during estradiol valerate model of PCO, yet, there were no available studies examining thyroid gland function and histology. Therefore, the present study aimed to investigate linkage between estradiol valerate-induced PCO and the development of thyroid dysfunction in rats. The study comprises 2 groups of male Wistar rats (n = 12), control group and PCO group. PCO was induced by injecting two doses of estradiol valerate with 6 weeks lag period in between. After twelve weeks, PCO was confirmed by vaginal smear examination which showed marked vaginal cornification. In addition, the light microscopic examination of the ovaries revealed chief histological signs of PCO like numerous cysts and damaged follicles. In addition, PCO-induced rats showed decreased serum LH and increased serum FSH levels. Thyroid hypoactivity was confirmed by increased serum TSH and decreased serum thyroid hormones (T3, and T4). Histologically, the thyroid tissue revealed small-size follicles devoid of the colloid and increased connective tissue between follicles. Semithin sections showed hypertrophied and/or flat follicular cells as well as increased resorption colloidal granules. Ultrathin sections showed low height cells with dark nucleus and heterochromatin. Furthermore, PCO-induced rats thyroid gland tissue revealed increased expression of the apoptotic mediator caspase-3. There was also a decrease in the expression of proliferating cell nuclear antigen. In summary, this study provides several effective biochemical and histological evidences for thyroid gland dysfunction in PCO-induced rats.