Dataset Information

Timing of levothyroxine administration affects serum thyrotropin concentration.

ABSTRACT:

Context

Patients treated with levothyroxine typically ingest it in a fasting state to prevent food impairing its absorption. The serum thyrotropin concentration is the therapeutic index of levothyroxine action.

Objective

The study objective was to determine the effect of the timing of levothyroxine administration in relationship to food on serum thyrotropin levels.

Design

Participants were randomized to one of six sequences, each consisting of three 8-wk regimens in a three-period crossover design. These regimens were in a fasting state, at bedtime, and with breakfast. The concentrations of TSH, free T(4), and total T(3) during each of the three timing regimens were documented. The primary outcome was the difference between serum TSH concentrations under fasting conditions compared with concentrations during the other 8-wk regimens.

Setting

The study was conducted in an academic medical center.

Participants

Study participants were receiving levothyroxine for treatment of hypothyroidism or thyroid cancer.

Results

Sixty-five patients completed the study. The mean thyrotropin concentration was 1.06 +/- 1.23 mIU/liter when levothyroxine was administered in the fasting state. When levothyroxine was taken with breakfast, the serum thyrotropin concentration was significantly higher (2.93 +/- 3.29 mIU/liter). When levothyroxine was taken at bedtime, the serum TSH concentration was also significantly higher (2.19 +/- 2.66 mIU/liter).

Conclusion

Nonfasting regimens of levothyroxine administration are associated with higher and more variable serum TSH concentrations. If a specific serum TSH goal is desired, thereby avoiding iatrogenic subclinical thyroid disease, then fasting ingestion of levothyroxine ensures that TSH concentrations remain within the narrowest target range.

SUBMITTER: Bach-Huynh TG

PROVIDER: S-EPMC2758731 | biostudies-literature | 2009 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Timing of levothyroxine administration affects serum thyrotropin concentration.

Bach-Huynh Thien-Giang TG Nayak Bindu B Loh Jennifer J Soldin Steven S Jonklaas Jacqueline J

The Journal of clinical endocrinology and metabolism 20090707 10

<h4>Context</h4>Patients treated with levothyroxine typically ingest it in a fasting state to prevent food impairing its absorption. The serum thyrotropin concentration is the therapeutic index of levothyroxine action.<h4>Objective</h4>The study objective was to determine the effect of the timing of levothyroxine administration in relationship to food on serum thyrotropin levels.<h4>Design</h4>Participants were randomized to one of six sequences, each consisting of three 8-wk regimens in a three ...[more]

PMID: 19584184

Similar Datasets

Project description:ImportanceWhether the use of generic vs brand levothyroxine affects thyrotropin levels remains unclear.ObjectiveTo compare the effectiveness of generic vs brand levothyroxine in achieving and maintaining normal thyrotropin levels among new users.Design, setting, and participantsThis retrospective, 1:1 propensity score-matched longitudinal cohort study used the OptumLabs Data Warehouse administrative claims database linked to laboratory results from commercially insured and Medicare Advantage enrollees throughout the United States. Eligible patients were adults (aged ≥18 years) with thyrotropin levels ranging from 4.5 to 19.9 mIU/L who initiated use of generic or brand-name levothyroxine from January 1, 2008, to October 1, 2017. Data were analyzed from August 13, 2018, to October 25, 2019.ExposurePatients received generic or brand-name levothyroxine.Main outcomes and measuresProportion of patients with normal vs markedly abnormal thyrotropin levels (<0.1 or >10 mIU/L) within 3 months and with stable thyrotropin levels within 3 months after the thyrotropin value fell into the normal range.ResultsA total of 17 598 patients were included (69.0% female; 74.0% White; mean [SD] age, 55.1 [16.0] years), of whom 15 299 filled generic and 2299 filled brand-name levothyroxine prescriptions during the study period. Among 4570 propensity score-matched patients (mean [SD] age, 50.3 [13.8] years; 3457 [75.6%] female; 3510 [76.8%] White), the proportion with normal thyrotropin levels within 3 months of filling levothyroxine prescriptions was similar for patients who received generic vs brand-name levothyroxine (1722 [75.4%; 95% CI, 71.9%-79.0%] vs 1757 [76.9%; 95% CI, 73.4%-80.6%]; P = .23), as was the proportion with markedly abnormal levels (94 [4.1%; 95% CI, 3.4%-5.0%] vs 88 [3.9%; 95% CI, 3.1%-4.7%]; P = .65). Among 1034 propensity score-matched patients who achieved a normal thyrotropin value within 3 months of initiation of levothyroxine, the proportion maintaining subsequent normal thyrotropin levels during the next 3 months was similar for patients receiving generic vs brand-name levothyroxine (427 [82.6%] vs 433 [83.8%]; P = .62).Conclusions and relevanceInitiation of generic vs brand-name levothyroxine formulations was associated with similar rates of normal and stable thyrotropin levels. These results suggest that generic levothyroxine as initial therapy for mild thyroid dysfunction is as effective as brand-name levothyroxine.

Project description:Background and aimWe have previously shown in a retrospective analysis that the plasma thyroid-stimulating hormone (TSH) rises significantly post-Ramadan in levothyroxine-treated hypothyroid patients, possibly as a result of lifestyle alterations and time restrictions during the nonfasting period from dusk until dawn. The aim of this study is to determine the best time to instruct patients to take levothyroxine during Ramadan so as to minimize changes in thyroid function tests during this period.MethodsIn a randomized prospective design, hypothyroid patients taking levothyroxine were randomized to receive instructions to take levothyroxine at one of the following 3 times during Ramadan: (group 1) at dusk 30-min before Iftar meal, (group 2) 3 or more hours after Iftar meal, or (group 3) at dawn 30-min before Suhur meal. Thyroid function tests were performed within 3 months before Ramadan and within 6 weeks post-Ramadan. Data from patients with at least 1 blood test before or after Ramadan were analyzed using mixed-effects regression models.ResultsPlasma TSH levels were available at one or more time points for 148 patients, group 1 (n = 50), group 2 (n = 46), and group 3 (n = 52). A statistically significant within-patient increase in plasma TSH was seen in patients at the 25th percentile pre-Ramadan in groups 2 and 3 (p values <0.001), but not in group 1. A statistically significant within-patient decrease in plasma TSH was found in patients at the 75th percentile in group 1 only. For patients at the 50th percentile pre-Ramadan, no statically significant within-patient changes were found, though descriptively, increases in plasma TSH were observed for groups 2 and 3, while a decrease was observed in group 1.ConclusionsOur data suggest that instructing patients to take levothyroxine at the time of breaking the fast 30 min before the Iftar meal minimizes unfavorable changes in plasma TSH post-Ramadan. In contrast, instructing patients to take levothyroxine 3 h post-Iftar or 30 min before Suhur led to a greater rise in post-Ramadan TSH.

Dataset Information

Timing of levothyroxine administration affects serum thyrotropin concentration.

Context

Objective

Design

Setting

Participants

Results

Conclusion

Publications

Timing of levothyroxine administration affects serum thyrotropin concentration.

Similar Datasets

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