Massa
03-12-2010, 01:04 AM
I have recently revisited my daily nutrient intake and realized that I get relatively low amounts of Vitamin A (but high amounts of Beta-Carotine) in my diet. Since I knew that people being hypothyroid have a hard time converting the carotine to retinol, I did some research on pubmed.com and came up with a bunch of articles on the connection between thyroid function and vitamin A. I will post one of them to encourage a discussion on whether low vitamin A could be a vicious circle for hypothyroid (or borderline hypothyroid) people, i.e. low Vit A leading to low T3 levels which in turn reduce the conversion of beta carotine and lowers vit A even further ...
Retinoic acid effects on thyroid function of female rats.
Silva AC, Marassi MP, Mühlbauer M, Lourenço AL, Carvalho DP, Ferreira AC.
Laboratório de Fisiologia Endócrina from Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
AIMS: Retinoic acid is widely used in dermatological treatment and thyroid cancer management; however its possible side-effects on normal thyroid function remains unknown. We aimed to determine the effects of retinoic acid on thyroid function of adult female rats. MAIN METHODS: Female Wistar rats were treated with all-trans-retinoic acid and 13-cis retinoic acid for 14 and 28 days. Then, rats were killed and thyroid function was evaluated. KEY FINDINGS: Serum T4 and thyrotropin levels remained unchanged, while serum T3 increased in animals treated with all-trans-retinoic acid for 14 days. No changes were observed in hepatic or renal type 1 iodothyronine deiodinase (D1) activities, while thyroid D1 was higher in animals treated for 14 days with all-trans-retinoic acid, which could be related to the increased serum T3 levels. 13-cis retinoic acid increased thyroid iodide uptake after 28 days. These results show effects of retinoic acid treatment on these thyroid proteins: sodium/iodide symporter and deiodinase. SIGNIFICANCE: Retinoic acid is able to interfere with normal thyroid function, increasing thyroid type 1 deiodinase activity, serum T3 levels and sodium/iodide symporter function. However, the effects are time- and retinoic acid isomer-dependent. Since serum thyrotropin levels did not change in any group, the effects observed are probably mediated by a direct retinoic acid effect on the normal thyroid.
Retinoic acid effects on thyroid function of female rats.
Silva AC, Marassi MP, Mühlbauer M, Lourenço AL, Carvalho DP, Ferreira AC.
Laboratório de Fisiologia Endócrina from Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
AIMS: Retinoic acid is widely used in dermatological treatment and thyroid cancer management; however its possible side-effects on normal thyroid function remains unknown. We aimed to determine the effects of retinoic acid on thyroid function of adult female rats. MAIN METHODS: Female Wistar rats were treated with all-trans-retinoic acid and 13-cis retinoic acid for 14 and 28 days. Then, rats were killed and thyroid function was evaluated. KEY FINDINGS: Serum T4 and thyrotropin levels remained unchanged, while serum T3 increased in animals treated with all-trans-retinoic acid for 14 days. No changes were observed in hepatic or renal type 1 iodothyronine deiodinase (D1) activities, while thyroid D1 was higher in animals treated for 14 days with all-trans-retinoic acid, which could be related to the increased serum T3 levels. 13-cis retinoic acid increased thyroid iodide uptake after 28 days. These results show effects of retinoic acid treatment on these thyroid proteins: sodium/iodide symporter and deiodinase. SIGNIFICANCE: Retinoic acid is able to interfere with normal thyroid function, increasing thyroid type 1 deiodinase activity, serum T3 levels and sodium/iodide symporter function. However, the effects are time- and retinoic acid isomer-dependent. Since serum thyrotropin levels did not change in any group, the effects observed are probably mediated by a direct retinoic acid effect on the normal thyroid.