Histological and immunohistochemical study of the effect of experimentally induced hypothyroidism on the thyroid gland and bone of male albino rats

Abstract

Background Hyperstimulation of follicular cells using a goitrogen [propylthiouracil (PTU)] caused thyroid dysfunctions that were associated with disturbances in adult bone turnover. Aim of the work This work was carried out to study the probable relationship between follicular and parafollicular cells in drug-induced hypothyroidism caused by PTU and consequently its effect on bone. Materials and methods The present work was carried out on 30 adult male albino rats divided into three groups. Group I was the control group; group II (the hypothyroid group) rats received PTU orally at a daily dose of 16.875 mg/rat of an average weight of 180 g for 4 weeks; group III was the recovery group. Thyroid glands were examined using histological and immunohistochemical techniques for calcitonin Ab-2. The midshaft of the femur bones of the studied groups was prepared and stained with H&E. Results In hypothyroid rats both follicular and C cells displayed signs of hyperactivity as the mean follicular cell height was significantly increased (P<0.05) compared with the control group. Moreover, the calcitonin immunoreactive cells showed a significant increase (P<0.05) in the mean values of their height and mean area% and number compared with the control group. These findings were reflected on bone sections in terms of a significant increase (P<0.05) in cortical bone thickness and a significant narrowing (P<0.05) of the Haversian canals when compared with the control group. Conclusion It could be concluded that C cells are not exclusively involved in calcium regulation independent of follicular cell activity; however, these cells interact with the surrounding follicular cells, enabling more effective coordinated functions between the two endocrine populations. Moreover, experimentally induced hypothyroidism resulted in increased C-cell number, consequently decreasing bone resorption and increasing cortical bone thickness.