Testosterone and estradiol treatments differently affect pituitary-thyroid axis and liver deiodinase 1 activity in orchidectomized middle-aged rats

• Published in: Experimental gerontology Vol. 72; pp. 85 - 98
• Main Authors: Šošić-Jurjević, B., Filipović, B., Renko, K., Miler, M., Trifunović, S., Ajdžanovič, V., Kӧhrle, J., Milošević, V.
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 01-12-2015
• Subjects: Aging; Animals; Body Weight; Estradiol; Estradiol - administration & dosage; Estradiol - analogs & derivatives; Immunohistochemistry; Iodide Peroxidase - metabolism; Liver - drug effects; Liver - enzymology; Male; Middle age; Orchiectomy; Pituitary Gland - pathology; Pituitary-thyroid axis; Rat; Rats; Rats, Wistar; Testosterone; Testosterone - administration & dosage; Thyroid Gland - pathology; Thyrotropin - blood; Thyroxine - blood; Orx-MA; Rat; E; IHC; HRP; IFC; YA; TRH; Orx-YA; Estradiol; SD; Tg; Pituitary-thyroid axis; MA; Orx; T; Tg-T4; SO; T3; PBS; T4; OrxPBS; Middle age; DAB; VEGF; Dio1; Dio2; TSH; RIA; ROI; RIF; Testosterone; TST; TH; NIS; TEM; RER
• ISSN: 0531-5565; 1873-6815
• DOI: 10.1016/j.exger.2015.09.010

We previously reported that orchidectomy (Orx) of middle-aged rats (15–16-month-old; MA) slightly affected pituitary-thyroid axis, but decreased liver deiodinase (Dio) type 1 and pituitary Dio2 enzyme activities. At present, we examined the effects of subsequent testosterone-propionate treatment (5mg/kg; Orx+T), and compared the effects of testosterone with the effects of estradiol-dipropionate (0.06mg/kg; Orx+E) treatment. Hormones were subcutaneously administered, daily, for three weeks, while Orx and sham-operated (SO) controls received only the vehicle. The applied dose of T did not alter serum TSH, T4 and T3 concentrations in Orx- MA, though it increased TSH when administrated to Orx young adults (2.5-month-old; Orx-YA). However, pituitaries of Orx–MA+T rats had higher relative intensity of immunofluorescence (RIF) for TSHβ; in their thyroids we found increased volume and height of follicular epithelium, decreased volume of the colloid and higher RIF for T4-bound to thyroglobulin (Tg-T4). Liver Dio1 activity was increased. E-treatment did not affect serum hormone levels, pituitary RIF for TSHβ, or liver Dio1 activity in Orx-MA rats. Thyroids had decreased relative volume and height of follicular epithelium, increased relative volume of the colloid, decreased volume of sodium-iodide symporter-immunopositive epithelium and lower RIF for Tg-T4. Detected changes were statistically significant. In conclusion, androgenization enhanced pituitary TSHβ RIF, thyroid activation and liver Dio1 enzyme activity in Orx-MA, without elevating serum TSH as in Orx-YA rats. Estrogenization induced pituitary enlargement with no effect on pituitary TSHβ RIF, serum TSH or liver Dio1 activity. E also induced alterations in thyroid histology that indicate mild suppression of its functioning, and contributed to thyroid blood vessel enlargement in Orx-MA rats.
•Androgenization or estrogenization of Orx-MA rats did not affect serum TSH, T4 and T3.•However, T-treatment enhanced pituitary TSHβ RIF, thyroid and liver Dio1 activity.•Estrogenization induced pituitary enlargement without affecting on pituitary TSHβ RIF.•In the thyroid, E induced mild suppressive changes and caused blood vessel enlargement.•E-treatment of Orx-MA rats did not affect liver Dio 1 activity.