Effects of Amiodarone on Thyroid Iodine Metabolism in Vitro1)

Abstract

Since alterations of thyroid function have been reported in patients treated with amiodarone, 2-butyl,3-(4-diethylaminoethoxy-3,5-diiodo, benzoyl) benzofuran, the effects of this drug on the active iodide transport, organic iodine formation, thyroid peroxidase and the enzymatic iodotyrosine deiodination, were studied. In pig thyroid slices the iodide transport was affected by amiodarone at concentrations of 10\m=-\4m and 10\m=-\5 M, showing a decrease of T/M (tissue/medium) ratios of 20 % and 23 %, respectively. Lower concentrations produced no significant differences from the controls. Iodotyrosine synthesis was only, but poorly, affected by 10\m=-\4 m and 10\m=-\5 m amiodarone. Inhibition of the DIT formation was greater than that produced for MIT. Thyroid peroxidase activity, as measured by the tyrosine-iodinase assay, showed a 20 % decrease at 10\m=-\3 m amiodarone. None of the other concentrations have affected the activity of the enzyme, except for 7 % at a concentration of 10\m=-\4 m. The iodotyrosine deiodination was affected by amiodarone only at a concentration of 10\m=-\3 m and 10\m=-\4 m. The inhibitions were of 22.5 % and 16.8 %, respectively. We have concluded that, under the conditions of our study, amiodarone per se does not affect the intrathyroidal iodine metabolism in concentrations which are usually present in the sera of patients treated with this drug. However, it is not possible to rule out an in vivo direct action, if amiodarone is substantially concentrated in the human thyroid gland.

Amiodarone Iodine‐induced Hypothyroidism: Risk Factors and Follow‐up in 28 Cases

“…The cause of thyroid failure in AIIH patients without underlying thyroid abnormalities and/or circulating anti-thyroid antibodies remains unknown. AIIH in these patients may be due to increased intrathyroidal iodine from iodine released by the deiodination of amiodarone, since the drug itself does not possess direct inhibitory action on thyroid hormone synthesis (Gluzman et al, 1977). Normally, the administration of large amounts of iodone results in a transient decrease of thyroid hormone synthesis, a phenomenon known as the acute Wolff-Chaikoff effect (Wolff et al, 1949).…”

Amiodarone compared with iodine exhibits a potent and persistent inhibitory effect on TSH-stimulated cAMP production in vitro: a possible mechanism to explain amiodarone-induced hypothyroidism

“…Gathering all the available data on the effects of AMD such as inhibition of TSH-stimulated cAMP production (5), diminished thyroid hormone secretion (37) and iodine metabolism (38), the effects on peripheral thyroid hormone metabolism (39)(40)(41) and effects on thyroid hormone receptors (41) may provide a mechanism for the development of hypothyroidism in some patients receiving AMD (3). Additionally the effects of AMD on cell viability are also important.…”

Αλληλεπιδραση Κατεχολαμινων Φαρμακων Που Δρουν Στους Υποδοχεις Των Κατεχολαμινων Και Φαρμακων Που Επηρεαζουν Την Διακινηση Ασβεστιου Σε Απομονωμενη Αορτη Επιμυος. Διερευνηση Της Δρασεως Της Αμιωδαρονης

“…Σάν ανεπιθύμητες ενέργειες αναφέρονται (Peter et al, 1983' Har ris et al, 1983a) δυσλειτουργίες του θυρεοειδούς (1-2%) μέ ύπερ-ή υποθυρεοειδισμό (Singh et al, 1983b), πνευμονική κυψελίτιδα (0-1%), επιβάρυνση ηπατικής λειτουργίας (0-10%), περιφερικές νευρολογικές διαταραχές (1%) και σέ παθολονοανατομικό επίπεδο μικροεναποθέσεις στους ιστούς του σώματος, πού φαίνεται νά αποτελούνται άπό τό φάρ μακο (Kumana και Hamer, 1979' Harris et al, 1983b. "Αν και ή επίδρα ση της άμιωδαρόνης στό καρδιακό δυναμικό ένερνείας, πού μιμείται τό αντίστοιχο ήλεκτροφυσιολογικό αποτέλεσμα του υποθυρεοειδισμού, εξου δετερώνεται άπό τήν θυροξίνη, γενικό ύποθυρεοειδικό αποτέλεσμα άπό τή χρήση άμιωδαρόνης δέν παρατηρείται συνήθως ούτε στον άνθρωπο οϋτε στά ζώα, οπως δέν παρατηρείται και άμεση επίδραση τοϋ φαρμάκου ε πί του θυρεοειδούς άδενος και του ένδοθυρεοειδικου μεταβολισμού τοϋ ιωδίου (Prichard et al, 1975' Gluzman et al, 1977.…”