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This study was a prospective, single-center, open-label, non-randomized, pharmacokinetic study using stable isotope carbon-13 labeled levothyroxine
Setting The study was conducted on the clinical research unit of an academic medical center.
Participants Adults of any age being treated with levothyroxine for hypothyroidism were studied.
Interventions A single dose of 13C- LT4 was administered to hypothyroid subjects taking levothyroxine replacement.
Main Outcomes and Measures Eighteen serial plasma samples were collected. One sample was obtained before the 13C- LT4 dose and the remainder over the 312-hour period post-dosing. 13C- LT4 concentration was quantified using validated liquid chromatography tandem mass spectrometry methods. Pharmacokinetic analysis was conducted using linear log trapezoidal non-compartmental analysis using Phoenix 6.4.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Stable isotope arm | Experimental | Measurement of blood levels of labelled levothyroxine after administration of single oral dose of stable isotope levothyroxine |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Administration of stable Isotope labeled levothyroxine | Drug | Administration of single dose of stable isotope carbon-13 labeled levothyroxine and measurement of blood levels of stable isotope-labeled levothyroxine |
| Measure | Description | Time Frame |
|---|---|---|
| CL/F | oral clearance rate (defined as the ratio of dose administered to AUC0-∞) | 120 hours |
| V/F | apparent volume of distribution (estimated by CL/F/ λ) | 120 hours |
| t-half | the half-life of the terminal disposition phase (t-half) estimated by ln(2)/λ . | 120 hours |
| Measure | Description | Time Frame |
|---|---|---|
| CL/F analysed by age groups | CL/F will be compared in adults (age ≤60 years) versus elderly (age>60 years) using Wilcoxon signed-rank test using significance level of α = 0.05. Additionally, these PK parameters were regressed against age (as a continuous covariate). Sex (male or female), weight (as a continuous covariate), and body mass index (BMI) (as a continuous covariate) will be considered using a stepwise linear regression approach. |
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Inclusion Criteria:
Exclusion Criteria:
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| ID | Term |
|---|---|
| D007037 | Hypothyroidism |
| ID | Term |
|---|---|
| D013959 | Thyroid Diseases |
| D004700 | Endocrine System Diseases |
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| ID | Term |
|---|---|
| D013974 | Thyroxine |
| ID | Term |
|---|---|
| D013963 | Thyroid Hormones |
| D006728 | Hormones |
| D006730 | Hormones, Hormone Substitutes, and Hormone Antagonists |
| D024322 | Amino Acids, Aromatic |
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Open label prospective study
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|
| 120 hours |
| V/F analysed by age groups | V/F will be compared in adults (age ≤60 years) versus elderly (age>60 years) using Wilcoxon signed-rank test using significance level of α = 0.05. Additionally, these PK parameters were regressed against age (as a continuous covariate). Sex (male or female), weight (as a continuous covariate), and body mass index (BMI) (as a continuous covariate) will be considered using a stepwise linear regression approach. | 120 hours |
| t-half by age groups | t-half will be compared in adults (age ≤60 years) versus elderly (age>60 years) using Wilcoxon signed-rank test using significance level of α = 0.05. Additionally, these PK parameters were regressed against age (as a continuous covariate). Sex (male or female), weight (as a continuous covariate), and body mass index (BMI) (as a continuous covariate) will be considered using a stepwise linear regression approach. | 120 hours |
| D000598 | Amino Acids, Cyclic |
| D000596 | Amino Acids |
| D000602 | Amino Acids, Peptides, and Proteins |