Thyrotropin hyperresponsiveness to TRH despite hyperthyroxinemia in amiodarone-treated subjects

Rao, R. Govinda; Buckell, H.M.; Rege, Vaijayanti P.; Spathis, G.S.

doi:10.1016/0026-0495(87)90030-8

“…Only a few studies (10,11) have investigated the early effects of amiodarone on thyroid function. One study was performed in nine healthy young adult subjects (all men, aged 25-40 yr), who received 400 mg per os for 28 days (10).…”

Section: Discussionmentioning

confidence: 99%

“…Earlier prospective studies on short-term effects of amiodarone have been limited to a small number of normal sub-jects rather than cardiac patients (10,11), and/or did not include data on free hormone concentrations when performed in arrhythmic patients (12). Furthermore, most data (10 -12) on TSH release were based on relatively a insensitive RIA method and/or TRH test, which was performed under basal condition and after 4 (10) or 24 (11) weeks of treatment, respectively.…”

mentioning

confidence: 99%

Acute Effects of Amiodarone Administration on Thyroid Function in Patients with Cardiac Arrhythmia

Iervasi

¹

,

Clerico

²

,

Bonini

³

et al. 1997

The Journal of Clinical Endocrinology & Metabolism

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Because little has been published on early effects of treatment with amiodarone on thyroid function, we studied serum total and free thyroid hormone, reverse T3, and TSH levels in patients with cardiac arrhythmias during the first 10 days of treatment with a loading dose of amiodarone by iv infusion. Twenty-four patients were enrolled in the study. A standardized loading regimen for the i.v. infusion of amiodarone was used. The protocol provided the i.v. infusion of 20 mg/kg per day on day 1, the i.v. infusion of 10 mg/kg per day on day 2, then 600 mg/day per os for 7-10 days, and finally, in patients chronically treated with the drug, the dose was gradually reduced to 400-200 mg/day per os. Total and free concentrations of T4 tended to progressively and significantly increase (P < 0.0001 repeated measures ANOVA) starting from the fourth day of therapy, whereas total T3 decreased from the second day progressively (P < 0.0001) throughout the study; free T3 did not significantly change. TSH levels early and significantly (P < 0.001, by ANOVA) increased throughout the study, starting from the first day of therapy and reaching at 10 days a value 2.7 times higher than the basal value. Reverse T3 levels progressively and significantly (after 2 days of treatment) increased and paralleled the TSH values, reaching at the 10th day a value about 2 times higher than basal value. In conclusion, our data suggest that after i.v. treatment with amiodarone: 1) TSH is the first hormone to change significantly followed by reverse T3, T4, and T3; 2) the progressive fall of T3 levels reflects an inhibition of the peripheral conversion of T4 to T3; 3) the observed later increase of total and free T4 levels may be explained by a contribution of direct thyroidal stimulation by TSH and/or by a reduction in T4 clearance.

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“…Only a few studies (10,11) have investigated the early effects of amiodarone on thyroid function. One study was performed in nine healthy young adult subjects (all men, aged 25-40 yr), who received 400 mg per os for 28 days (10).…”

Section: Discussionmentioning

confidence: 99%

“…Earlier prospective studies on short-term effects of amiodarone have been limited to a small number of normal sub-jects rather than cardiac patients (10,11), and/or did not include data on free hormone concentrations when performed in arrhythmic patients (12). Furthermore, most data (10 -12) on TSH release were based on relatively a insensitive RIA method and/or TRH test, which was performed under basal condition and after 4 (10) or 24 (11) weeks of treatment, respectively.…”

mentioning

confidence: 99%

Acute Effects of Amiodarone Administration on Thyroid Function in Patients with Cardiac Arrhythmia

Iervasi

¹

1997

Journal of Clinical Endocrinology & Metabolism

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Because little has been published on early effects of treatment with amiodarone on thyroid function, we studied serum total and free thyroid hormone, reverse T3, and TSH levels in patients with cardiac arrhythmias during the first 10 days of treatment with a loading dose of amiodarone by iv infusion. Twenty-four patients were enrolled in the study. A standardized loading regimen for the i.v. infusion of amiodarone was used. The protocol provided the i.v. infusion of 20 mg/kg per day on day 1, the i.v. infusion of 10 mg/kg per day on day 2, then 600 mg/day per os for 7-10 days, and finally, in patients chronically treated with the drug, the dose was gradually reduced to 400-200 mg/day per os. Total and free concentrations of T4 tended to progressively and significantly increase (P < 0.0001 repeated measures ANOVA) starting from the fourth day of therapy, whereas total T3 decreased from the second day progressively (P < 0.0001) throughout the study; free T3 did not significantly change. TSH levels early and significantly (P < 0.001, by ANOVA) increased throughout the study, starting from the first day of therapy and reaching at 10 days a value 2.7 times higher than the basal value. Reverse T3 levels progressively and significantly (after 2 days of treatment) increased and paralleled the TSH values, reaching at the 10th day a value about 2 times higher than basal value. In conclusion, our data suggest that after i.v. treatment with amiodarone: 1) TSH is the first hormone to change significantly followed by reverse T3, T4, and T3; 2) the progressive fall of T3 levels reflects an inhibition of the peripheral conversion of T4 to T3; 3) the observed later increase of total and free T4 levels may be explained by a contribution of direct thyroidal stimulation by TSH and/or by a reduction in T4 clearance.

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“…Além da queda dos níveis de T 3 intrapituitários, ocasionada pela inibição da 5'-iodotironina desiodase tipo 2, a amiodarona também age como um antagonista competitivo de T 3 em células pituitárias 70 , estimulando a liberação de TSH 79,80 . Esta elevação dos níveis circulantes de TSH e a diminuição da conversão de T 4 em T 3 são responsáveis pelo aumento dos níveis de T 4 séricos 81 (Figura 4).…”

Section: Antagonismo Competitivo De T 3 Em Células Pituitáriasunclassified

Distinção entre os tipos 1 e 2 de tireotoxicose associada à amiodarona por meio de dúplex-Doppler colorido

Macedo¹

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Thyrotropin hyperresponsiveness to TRH despite hyperthyroxinemia in amiodarone-treated subjects

Cited by 6 publications

References 25 publications

Acute Effects of Amiodarone Administration on Thyroid Function in Patients with Cardiac Arrhythmia

Acute Effects of Amiodarone Administration on Thyroid Function in Patients with Cardiac Arrhythmia

Acute Effects of Amiodarone Administration on Thyroid Function in Patients with Cardiac Arrhythmia

Distinção entre os tipos 1 e 2 de tireotoxicose associada à amiodarona por meio de dúplex-Doppler colorido

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