The Effect Of Chronic Intermittent Hypoxia On Hypothalamic-pituitary- Thyroid Axis In Rats

Objective:To set up a chronic intermittent hypoxic animal model, as an experimental platform for further study of the pathogenesis of OSAHS. To study the effect of chronic intermittent hypoxia and removal of hypoxia on hypothalamic-pituitary-thyroid axis in Sprague-Dawley rats, including changes of TRH, TSH, T3, T4 in blood serum and their interrelation, comparison of thyroid's weight, observing the ultrastructural changes in rats hypothalamus, pituitary and thyroid to approach the possible mechanisms of hypothalamic-pituitary-thyroid axis'dysfunction in patients with OSAHS, and to provide a theoretical basis for the treatment of patients with OSAHS.Methods:Experiments were performed on 24 three-month-old male Sprague-Dawley rats, they were randomly assigned to three experimental groups (n=8/group), included unhandled control group (UC), chronic intermittent hypoxia group (CIH), and Removal of hypoxia group (RH). Rats in UC group were raised normally, those in CIH group suffered 8H intermittent hypoxia everyday, the duration of experiment was 4 weeks, and those in RH group was the same as those in CIH group in previous 4 weeks and were raised normally in later 4 weeks. All the rats were killed after experiment. TRH, TSH, T3, T4 in serum of rats were measured by radioimmunity, and comparison of thyroid's weight of rats' were measured by electronic balance, ultramicrostructure of rats' hypothalamus, pituitary and thyroid were observed by electron microscope.Results:â‘ The level of the rats'TRH, TSH, T3, T4 in serum in the CIH group decreased significantly than those in the UC group and RH group (P<0.05), but it is not true between UC group and RH group (P>0.05).â‘¡The weight of the rats' thyroid in the CIH group increased significantly than those in the UC group and RH group (P<0.01), but it is not true between UC group and RH group (P>0.05).â‘¢Ultramicrostructures of rats' hypothalamus, pituitary and thyroid had light changes of hypoxia in the CIH group. In neuroendocrine cells of hypothalamus, there were light bioblast pyknosis, axoplasm engorge and wallerian degeneration in some medullated nerve fibers, superficial electro-dense in non-medullated nerve fibers. There were endocytoplasmic reticulum and bioblast engorge in basicyte of distal portion in pituitary. Thyroid follicle cells became shrinked and thyroid epithelial cells became lowered, parts of which had damaged shapes, and there were bioblast pykno sis, endocytoplasmic reticulum and Golgi complex engorge in the follicle cell of thyroid.But they were normal in UC group and RH group.Conclusions:Chronic intermittent hypoxia can lead rats' hypothalamic-pituitary- thyroid axis to abnormality and disorde r of feedback regulation, but restore hypoxia can make it normal.