Effects of gonadal hormones on thymus gland after bilateral ovariectomy in the rats: The light and electron microscopic study

64 6. SUMMARY The purpose of this study was to examine the histological changes that occured in the thymus gland after prepubertal and pubertal gonadectomy and the various sex steroids administration (testosterone, estrogen and progesterone) following prepubertal and pubertal gonadectomy. Wistar-Albino rats used in this study were divided into two main groups (Group A and Group B) each containing further subgroups. Group A included 6 weeks of age male and female rats, Group B included 12 weeks of age male and female rats. Male and female rats were performed bilateral gonadectomy. Effects of gonadal steroid hormones (testosterone, estrogen and progesterone) on the thymus gland were examined by light and electron microscopy. Thymic weight increased after gonadectomy at all the groups. Testosterone, estrogen, estrogen+progesterone treatment decreased thymic weight after gonadectomy. Progesterone treatment also decreased, but there was no statistically significant. In the light microscopy, testosterone and estrogen treatment, but not progesterone, loss of lymphoid elements from the thymic cortex occured significantly, which allowed the visualization of empty areas in which the epithelial cells became more evident. Apart from the changes above, increasing number of phagocytic macrophages and mast cells, enlarged blood vessels, connective tissue in the thymic medulla were observed in the thymus gland. In the electron microscopic study was observed enlargement rough endoplasmic reticulum in the thymic lymphocytes. The same observations were also found after estrogen+progesterone treatment. Significant changes were not histologically observed in the thymus gland after progesterone treatment. In conclusion, the study demonstrated that the thymus gland undergoes involution after testosterone and estrogen treatment, but not progesterone, following prepubertal and pubertal gonadectomy. The thymic involution resulted by estrogen and testosterone hormone treatment was due to decreasing of cortical lymphocytes in the thymic cortex.