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The pharmacodynamic equivalence of levothyroxine and liothyronine: a randomized, double blind, cross-over study in thyroidectomized patients.


ABSTRACT:

Context

The substitution of liothyronine (L-T3) for levothyroxine (L-T4) is commonly employed during thyroid hormone (TH) withdrawal in preparation for diagnostic and therapeutic interventions on thyroid cancer patients. Presently, only limited data are available on the L-T3 for L-T4 therapeutic substitution. Objective To characterize the pharmcodynamic equivalence of L-T3 and L-T4.

Design

Randomized, double-blind, cross-over intervention study.

Setting

NIH clinical center.

Patients

Ten thyroidectomized patients.

Interventions

Study participants were treated with L-T3 or L-T4 with a target TSH >or= 0.5 Main outcome measuresArea under the serum concentration-time curve of TSH from 0 to 60 min (AUC(0-60)) and peak TSH serum concentration (C(max)) following thyrotropin-releasing hormone (TRH) stimulation test, total L-T4 and L-T3 dose (mcg/kg), and L-T4/L-T3 ratio.

Results

No difference was observed for time 0 TSH values between L-T3 and L-T4 replacement phases (1.48 +/- 0.77 vs. 1.21 +/- 0.62 mU/l, P = 0.293) at average daily doses of 40.3 +/- 11.3 mcg L-T3 and 115.2 +/- 38.5 mcg L-T4, L-T3: L-T4 ratio 0.36 +/- 0.06. TRH stimulation test resulted in similar L-T3 vs. L-T4 TSH responses with AUC(0-60) of 326.1 (95% CI 232.6-457.1) and 247.1 (95% CI 153.8-397.1) mU* min/l (P = 0.285); and C(max) of 6.83 (95% CI 4.88-9.55) and 5.23 (95% CI 3.31-8.3) mU/l (P = 0.383).

Conclusions

This is the first study addressing the equivalency between L-T3 and L-T4 therapy measured by baseline and TRH-stimulated TSH. The therapeutic substitution of L-T3 for L-T4 was achieved at approximately 1:3 ratio.

SUBMITTER: Celi FS 

PROVIDER: S-EPMC2888764 | biostudies-literature | 2010 May

REPOSITORIES: biostudies-literature

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The pharmacodynamic equivalence of levothyroxine and liothyronine: a randomized, double blind, cross-over study in thyroidectomized patients.

Celi Francesco S FS   Zemskova Marina M   Linderman Joyce D JD   Babar Nabeel I NI   Skarulis Monica C MC   Csako Gyorgy G   Wesley Robert R   Costello Rene R   Penzak Scott R SR   Pucino Frank F  

Clinical endocrinology 20100501 5


<h4>Context</h4>The substitution of liothyronine (L-T3) for levothyroxine (L-T4) is commonly employed during thyroid hormone (TH) withdrawal in preparation for diagnostic and therapeutic interventions on thyroid cancer patients. Presently, only limited data are available on the L-T3 for L-T4 therapeutic substitution. Objective To characterize the pharmcodynamic equivalence of L-T3 and L-T4.<h4>Design</h4>Randomized, double-blind, cross-over intervention study.<h4>Setting</h4>NIH clinical center.  ...[more]

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