title: Estrogen effects on thyroid iodide uptake and thyroperoxidase activity in normal and ovariectomized rats.
abstract: Sex steroids interfere with the pituitary-thyroid axis function, although the reports have been controversial and no conclusive data is available. Some previous reports indicate that estradiol might also regulate thyroid function through a direct action on the thyrocytes. In this report, we examined the effects of low and high doses of estradiol administered to control and ovariectomized adult female rats and to pre-pubertal females. We demonstrate that estradiol administration to both intact adult and pre-pubertal females causes a significant increase in the relative thyroid weight. Serum T3 is significantly decreased in ovariectomized rats, and is normalized by estrogen replacement. Neither doses of estrogen produced a significant change in serum TSH and total T4 in ovariectomized, adult intact and pre-pubertal rats. The highest, supraphysiological, estradiol dose produced a significant increase in thyroid iodide uptake in ovariectomized and in pre-pubertal rats, but not in control adult females. Thyroperoxidase activity was significantly higher in intact adult rats treated with both estradiol doses and in ovariectomized rats treated with the highest estradiol dose. Since serum TSH levels were not significantly changed, we suggest a direct action of estradiol on the thyroid gland, which depends on the age and on the previous gonad status of the animal.
authors.affiliation: Laboratório de Fisiologia Endócrina, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil.
authors.forename: Lívia P
authors.initials: LP
authors.lastname: Lima
authors.forename: Inês A
authors.initials: IA
authors.lastname: Barros
authors.forename: Patrícia C
authors.initials: PC
authors.lastname: Lisbôa
authors.forename: Renata L
authors.initials: RL
authors.lastname: Araújo
authors.forename: Alba C M
authors.initials: AC
authors.lastname: Silva
authors.forename: Doris
authors.initials: D
authors.lastname: Rosenthal
authors.forename: Andrea C F
authors.initials: AC
authors.lastname: Ferreira
authors.forename: Denise P
authors.initials: DP
authors.lastname: Carvalho
mesh_terms: D000367:Age Factors; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D007453:Iodide Peroxidase / Q000097:blood / Q000378:metabolism*; D007455:Iodine / Q000493:pharmacokinetics*; D007456:Iodine Isotopes / Q000008:administration & dosage / Q000493:pharmacokinetics; D009929:Organ Size; D010052:Ovariectomy; D051381:Rats; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D013997:Time Factors
chemical_list: D007456:Iodine Isotopes; D004958:Estradiol; D013972:Thyrotropin; D007455:Iodine; D007453:Iodide Peroxidase; D013974:Thyroxine