The effects of chronic administration of 17β-estradiol dipropionate on the thyroid structure and function in rats.
Estradiol has been shown to affect normal thyroid structure and function, though previous reports have indicated both stimulatory and inhibitory effects. The current study examined the effect of the administration of high doses of 17β-estradiol dipropionate on the thyroid structure and function of eight three-month-old female Wistar rats over a three-week period. Rat thyroids were harvested after the injection period, sectioned at 7μm, mounted, and stained with hematoxylin and eosin. Stereological analysis was quantified with volume density – a measure of the sum of the volumes of a particular object in the thyroid divided by the sum of the total thyroid volume – and calculated with the use of the software package MetaMorph. All data was adjusted for varying weights of rats according to established correlations. There were no significant differences in the volume densities of the colloid, epithelia, follicle, or interstitium in the three regions of the thyroid studied. There was a significant decrease in the oxygen consumption of EDP-treated rats vs. control rats (p=0.002; EDP-treated = 42.07 kcal/m 2/hr; control = 73.73 kcal/m 2/hr). Though the present study was unable to demonstrate that estradiol modulates thyroid structure, oxygen consumption data demonstrates a suppressive effect of estradiol on thyroid function.