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Levothyroxine

T4 · Synthroid · Euthyrox · L-Thyroxine

Thyroid HormonesApproved
MW
776.87g/mol
Formula
C15H11I4NO4

Levothyroxine, also known as L-T4, is a synthetic form of the thyroid hormone thyroxine, produced primarily in the thyroid gland, which plays a crucial role in regulating metabolism and energy levels in the body. Researchers primarily study levothyroxine for its effects on thyroid function, particularly in individuals with hypothyroidism. Key findings from recent studies indicate that liquid and softgel formulations of L-T4 are more bioavailable than traditional tablet forms, resulting in lower serum thyrotropin (TSH) levels in hypothyroid patients. Additionally, clinical evidence suggests that L-T4 therapy may reduce carotid intima-media thickness in patients with subclinical hypothyroidism, potentially improving cardiovascular health. Current research continues to explore optimal administration methods and the broader implications of levothyroxine therapy in various populations, highlighting its clinical relevance in managing thyroid-related conditions.

Overview

Übersicht

Levothyroxine, also known as T4, Synthroid, or Euthyrox, is a synthetic form of the endogenous thyroid hormone thyroxine. It is produced by the thyroid gland in the body and belongs to the chemical class of thyroid hormones. Levothyroxine is commonly used as a replacement therapy in individuals with hypothyroidism, where the thyroid gland does not produce sufficient amounts of thyroxine. Researchers have extensively studied its role in managing thyroid hormone levels in patients with thyroid disorders. Levothyroxine plays a crucial role in regulating metabolism, growth, and development. It is involved in numerous physiological processes, including the regulation of protein synthesis and the maintenance of basal metabolic rate. Research areas include its effects on cardiovascular health, bone density, and metabolic functions. The mechanism of action of levothyroxine involves its conversion to triiodothyronine (T3), which then binds to thyroid hormone receptors in the cell nucleus. This binding initiates transcriptional changes that influence metabolic and developmental processes. Levothyroxine's pharmacokinetic properties include a long half-life of approximately 7 days, which allows for once-daily dosing. It is primarily metabolized in the liver and kidneys, and its bioavailability can vary depending on the formulation, with liquid and softgel capsules showing higher bioavailability compared to tablets. Clinically, levothyroxine is used to treat hypothyroidism and is approved by regulatory agencies worldwide. It is a prescription medication and is not classified as a controlled substance. Researchers have found it effective in normalizing thyroid hormone levels and alleviating symptoms of hypothyroidism, although careful monitoring is required to avoid overmedication.

Chemical profile

Chemische Struktur

Chemical structure of Levothyroxine
FormelC15H11I4NO4
Molekulargewicht776.87g/mol
CAS-Nummer51-48-9
PubChem CID5819
Mechanism

Wirkmechanismus

Levothyroxine acts primarily through conversion to triiodothyronine (T3), which binds to thyroid hormone receptors in the nucleus of target cells. This binding initiates transcriptional changes that regulate gene expression, influencing metabolic rate, protein synthesis, and growth processes.

Mechanism

Signalweg

Levothyroxine (L-T4) acts primarily through the thyroid hormone receptors (TRs), which are nuclear hormone receptors that regulate gene expression upon binding to L-T4. This binding activates the TRs, leading to the modulation of various signaling pathways, including the cAMP/PKA pathway and the regulation of metabolic processes such as lipid metabolism, protein synthesis, and thermogenesis. The precise mechanisms of action, particularly the full spectrum of downstream effects and interactions with other signaling pathways, remain incompletely understood.

Half-Life & Pharmacokinetics

ENEndogenous

Circulating half-life ~7 days

POOral

Bioavailability varies; liquid and softgel forms have higher bioavailability than tablets

The half-life allows for once-daily dosing. Bioavailability can be affected by gastrointestinal factors and concurrent medications.

Storage

Temperature

Store at room temperature (15-30C)

Light

Protect from light

Form

Tablets and capsules are stable under recommended storage conditions

Notes

Avoid exposure to excessive heat and moisture to maintain stability.

Solubility

Löslichkeit

Levothyroxine is poorly soluble in water, which affects its formulation and absorption characteristics.

Legal Status

🇩🇪DE

Verschreibungspflichtig (prescription only); not a controlled substance under BtMG.

🇺🇸US

FDA approved; prescription required; not a controlled substance.

🇦🇺AU

TGA S4 (prescription only medicine).

🇬🇧UK

Prescription only medicine (POM) under MHRA regulation.

Legal status information is provided for general reference only and may not reflect the most current regulatory changes. Always verify with official government sources before making any decisions.

Open Questions

Offene Forschungsfragen

Current evidence is limited regarding the optimal formulation of levothyroxine (L-T4) for different patient populations, particularly in those co-ingesting medications that impair absorption, as well as the long-term effects of L-T4 on carotid intima-media thickness in subclinical hypothyroidism. Further research is needed through larger randomized controlled trials (RCTs) to clarify the impact of L-T4 regimens during specific conditions, such as Ramadan fasting, and to establish comprehensive guidelines for TSH management in patients receiving L-T4 therapy. Additionally, studies focusing on the effects of L-T4 on unique presentations of hypothyroidism, such as ascites and malnutrition, are necessary to understand the broader implications of treatment adherence and dosage adjustments.

158 Research Publications

3,284

Total Citations

62

Human/RCT

2.7

Avg. Influence

2024

Latest

Sort
Filter
#01

Overt and subclinical hypothyroidism complicating pregnancy.

Case ReportInfluence25.0
731
The study demonstrated that adequate levothyroxine treatment during pregnancy significantly improves outcomes for women with overt or subclinical hypothyroidism, reducing risks of abortion and complications.
#02

Treatment of hypothyroidism.

ReviewInfluence7.0
168
The study demonstrated that effective management of hypothyroidism requires careful monitoring and gradual dosage adjustments of levothyroxine, especially in elderly patients.
#03

Gastrointestinal Malabsorption of Thyroxine.

ReviewInfluence9.0
140
The study demonstrated that gastrointestinal malabsorption is a significant cause of refractory hypothyroidism in patients on levothyroxine, necessitating careful monitoring and potential treatment adjustments.
#04

Defending plasma T3 is a biological priority.

ReviewInfluence3.0
131
The study demonstrated that maintaining stable serum T3 levels is crucial for thyroid hormone regulation, highlighting the potential need for combination therapy in patients with hypothyroidism who do not achieve symptom relief with levothyroxine alone.
#05

Monitoring thyroxine treatment during pregnancy.

Case ReportInfluence7.0
128
Researchers observed that serum TSH levels often rose above normal in human hypothyroid women during pregnancy despite constant levothyroxine doses, necessitating dose adjustments.
#06

The administration of L-thyroxine as soft gel capsule or liquid solution.

ReviewInfluence4.0
87
The review indicated that soft gel capsules and liquid formulations of levothyroxine may improve bioavailability and absorption compared to traditional tablets in human patients.
#07

Effects of Altering Levothyroxine (L-T4) Doses on Quality of Life, Mood, and Cognition in L-T4 Treated Subjects.

HumanInfluence2.0
72
#08

Prediction of thyroid hormone supplementation after thyroid lobectomy.

Case ReportInfluence3.0
68
The study demonstrated that preoperative TSH levels and the presence of microsomal antibodies are strong predictors of the need for postoperative levothyroxine supplementation in patients undergoing thyroid lobectomy.
#09

Hypothyroxinemia and pregnancy.

ReviewInfluence2.0
67
The study demonstrated that isolated hypothyroxinemia during pregnancy negatively impacts fetal brain development, highlighting the need for adequate iodine supplementation.
#10

Levothyroxine Interactions with Food and Dietary Supplements-A Systematic Review.

Wiesner Agnieszka, et al. · Pharmaceuticals (Basel, Switzerland) · 2021

ReviewInfluence3.0
67
The study demonstrated that food interactions can significantly affect levothyroxine absorption, suggesting that timing and formulation adjustments may be necessary to optimize treatment efficacy.

Key findings

  1. 01Levothyroxine can be taken in the morning or at bedtime with equal effectiveness.
  2. 02Certain foods and supplements, like coffee and calcium, can decrease levothyroxine absorption.
  3. 03Maintaining a time gap between levothyroxine and food intake can help avoid interactions.

Clinical Trials (95)

Preclinical
Phase I
Phase II
Phase III
Approved

95

Total Trials

22,870

Total Enrolled

Thyroid Disease in Pregnancy: Case Finding Versus Universal Screening

NCT00846755COMPLETED
Sponsor

Ospedale V. Fazzi

Enrollment

4,657

Started

2005

Primary outcome

number of adverse outcomes which occur during pregnancy and in the neonatal period in patients divided in Case Finding and Universal Screening groups

Thyroid DiseasePregnancy

The Effect of Thyroid Antibodies on Female Reproductive Function and Pregnancy Outcomes

Sponsor

Second Affiliated Hospital, Zhejiang University, School of Medicine

Enrollment

4,000

Started

2020

Primary outcome

Incidence rate of pregnancy complications in women with or without thyroid antibodies

Thyroiditis, Autoimmune

Effect of HCQ Combined With LT4 on LBR in Euthyroid Women With URPL and TPO-Ab

NCT06652113RECRUITING
Sponsor

Sun Yat-Sen Memorial Hospital of Sun Yat-Sen University

Enrollment

796

Started

2024

Primary outcome

Birth of a living child beyond 28 weeks

Recurrent Pregnancy LossEuthyroid With Thyroid Antibodies

Preconceptional Thyroid Screening and Childhood Nerocognitive Function

Sponsor

Fudan University

Enrollment

600

Started

2011

Primary outcome

Offspring neurocognitive assessment at 0-3 yrs

Hypothyroidism

Thyroid Hormone Replacement After Coronary Artery Bypass Grafting for Patients With Subclinical Hypothyroidism

NCT07380854RECRUITING
Sponsor

Seoul National University Bundang Hospital

Enrollment

338

Started

2022

Primary outcome

A composite of MACE within 4months after surgery

Subclinical Hypothyroidism

A Randomized Controlled Trial of Thyroid Hormone Supplementation in Hemodialysis Patients

NCT03977207RECRUITING
Sponsor

University of California, Irvine

Enrollment

336

Started

2020

Primary outcome

Health-Related Quality of Life (HRQOL) - Short Form 36 Physical Component Score

Thyroid; Functional DisturbanceHypothyroidismHemodialysis

Individual Dosing of Levothyroxine After Thyroidectomy

Sponsor

Second Affiliated Hospital, School of Medicine, Zhejiang University

Enrollment

202

Started

2022

Primary outcome

euthyroidism

Thyroid NeoplasmsHypothyroidismSurgery

Best Treatment for Women With Both (Polycystic Ovary Syndrome) PCOS and Subclinical Hypothyroidism

NCT06041204RECRUITING
Sponsor

Muhamed Ahmed Abdelmoaty Muhamed Alhagrasy

Enrollment

200

Started

2021

Primary outcome

Pregnancy rate

PCOS (Polycystic Ovary Syndrome) of Bilateral OvariesSubclinical HypothyroidismFemale Infertility

Thyroid and Adrenocortical Hormone Replacement in Organ Donors

NCT04528797COMPLETED
Sponsor

Medical University of South Carolina

Enrollment

199

Started

2010

Primary outcome

Change in Vasoactive Inotrope Score (VIS) score from beginning of active donor management until procurement.

Brain Death

Thyroid Lobectomy With or Without Levothyroxine Treatment Postoperatively

NCT00941551COMPLETED
Sponsor

Jagiellonian University

Enrollment

150

Started

2000

Primary outcome

Primary outcome measure was prevalence of recurrent goiter within the contralateral thyroid lobe

Recurrent Goiter

The Effects of T4 Versus T4/T3 on Psychological Distress After Total Thyroidectomy in Thyroid Cancer Patients

NCT03024151COMPLETED
Sponsor

Inje University

Enrollment

150

Started

2016

Primary outcome

Psychological distress (depression or anxiety) assessed with HADS

Thyroid CancerDistressDepressionAnxietyFatigue

Effect of Levothyroxine on Serum Adiponectin, Insulin Resistance and Cardiovascular Risk in Patients With Hypothyroidism

NCT02467244COMPLETED
Sponsor

All India Institute of Medical Sciences, Bhubaneswar

Enrollment

120

Started

2017

Primary outcome

Change of Serum Adiponectin from baseline

Hypothyroidism

SNUH Immune Checkpoint Inhibitor-induced Hypothyroidism Recovery Trial

NCT07421869RECRUITING
Sponsor

Seoul National University Bundang Hospital

Enrollment

107

Started

2024

Primary outcome

Proportion of participants who maintain discontinuation of levothyroxine for at least 6 months

Hypothyroidism

Thyroxine Supplementation in Small for Gestational Age (SGA) Infants With Birth Weight <1500g and TSH 6-20 mIU/ml

NCT07625722NOT_YET_RECRUITING
Sponsor

Shandong Provincial Hospital

Enrollment

106

Started

2026

Primary outcome

Cognitive function evaluated by Bayley-IV

Thyroid FunctionPretermSGA and GrowthNeurodevelopment Outcome

Quality of Life After Interventional Thyroid Treatment

NCT03880578COMPLETED
Sponsor

Klinikum Lüdenscheid

Enrollment

101

Started

2019

Primary outcome

ThyPRO Scale Scores (0-100, Higher Scores Indicating Worse Quality of Life)

Thyroid; DeficiencyQuality of Life

Efficacy of Thyroid Hormone Replacement for Secondary Hypothyroidism Following Intracerebral Hemorrhage

Sponsor

Peking Union Medical College Hospital

Enrollment

100

Started

2023

Primary outcome

blood pressure

Intracerebral HemorrhageLow T3 SyndromeNeurocritical CareHormone Replacement Therapy

Recovery Rate in Secondary Hypothyroidism

Sponsor

Nova Scotia Health Authority

Enrollment

90

Started

2022

Primary outcome

Percentage of patients achieving euthyroid status

Secondary Hypothyroidism

Safety and Efficacy of Empiric Levothyroxine (LT4) Dose Increase Versus Individualized LT4 Dose Increase in Hypothyroid Women During Pregnancy

NCT03115515COMPLETED
Sponsor

Medstar Health Research Institute

Enrollment

60

Started

2011

Primary outcome

% of TSH values within trimester-specific goal range per patient from study enrollment to delivery

Pregnancy RelatedThyroid

Wound Complications in Head and Neck Surgery

NCT03134976COMPLETED
Sponsor

University of Michigan

Enrollment

51

Started

2017

Primary outcome

Number of patients treated with Levothyroxine who develop pharyngocutaneous fistula after salvage laryngectomy

Hypothyroidism; SurgeryHead and Neck CancerWound HealLaryngeal CancerLaryngeal Fistula

Thyroid Hormone Dose Adjustment in Pregnancy

NCT00230802COMPLETED
Sponsor

Brigham and Women's Hospital

Enrollment

48

Started

2005

Primary outcome

Proportion of Patients in Each Treatment Arm Euthyroid Through Gestation

PregnancyHypothyroidism

Hypothyroidism, Metabolism and Quality of Life - Focus on QOL, REE, Cognitive Function and Body Composition

NCT02891668COMPLETED
Sponsor

Herlev Hospital

Enrollment

42

Started

2015

Primary outcome

Changes in quality of life as measured with the ThyPro questionaire

Hypothyroidism

Levothyroxine Treatment on Cardiac Function in Children With Subclinical Hypothyroidism

NCT07393165RECRUITING
Sponsor

Tanta University

Enrollment

40

Started

2025

Primary outcome

Assessment of left ventricle systolic function

LevothyroxineCardiac FunctionChildrenSubclinical Hypothyroidism

Thyroid Hormone Replacement After Radio Iodine: Value and Efficacy

NCT06647602NOT_YET_RECRUITING
Sponsor

University Medical Center Groningen

Enrollment

40

Started

2026

Primary outcome

TSH after two weeks of TH substitution

Differentiated Thyroid CancerThyroid CancerLevothyroxineLiothyronineThyroid Hormones

The Effect of Levothyroxine on Arterial Stiffness and Lipid Profile in Patients With Subclinical Hypothyroidism

NCT00498238COMPLETED
Sponsor

Assaf-Harofeh Medical Center

Enrollment

34

Started

2003

Subclinical Hypothyroidism

Generic vs. Name-Brand Levothyroxine

NCT00403390COMPLETED
Sponsor

Boston Children's Hospital

Enrollment

34

Started

2006

Primary outcome

Thyroid Stimulating Hormone as Primary Endpoint Measured at Initiation of Study, After 8 Weeks of One Drug, and Then 8 Weeks After the Second Drug.

Congenital HypothyroidismHypothyroidism

Targeted Levothyroxine Dosing in Infants With Congenital Hypothyroidism

NCT02374593COMPLETED
Sponsor

Erica Eugster

Enrollment

24

Started

2014

Primary outcome

Dose Adjustments

Congenital Hypothyroidism

Metabolic Changes in Hypothyroid Patients

NCT00524238COMPLETED
Sponsor

University of Aarhus

Enrollment

22

Started

2004

Hypothyroidism

Hypothyroidism, Metabolism and Food Intake

NCT02993562COMPLETED
Sponsor

Herlev Hospital

Enrollment

18

Started

2015

Primary outcome

Changes in food intake at ad libitum meal

Hypothyroidism

Is Levothyroxine Alone Adequate Thyroid Hormone Replacement?

NCT02567877TERMINATED
Sponsor

University of Colorado, Denver

Enrollment

12

Started

2016

Primary outcome

Change in working memory (N-back testing) and correlation with deiodinase type 2 polymorphism

Postsurgical HypothyroidismHypothyroidism

Improving White Matter Integrity With Thyroid Hormone

NCT04098991COMPLETED
Sponsor

University of Illinois at Chicago

Enrollment

5

Started

2017

Primary outcome

High Angular Diffusion Tensor Imaging

Hypothyroidism

LISA-study : Levothyroxin in Nodular Goiter

NCT00277589Phase 4COMPLETED
Sponsor

Sanofi

Enrollment

1,024

Started

2004

Primary outcome

The primary outcome measure is to compare the change in total volume of all nodules after 12 months Levothyroxin treatment to the change after 12 months of each of the reference treatments (one of the two active controls or placebo)

Goiter, Nodular

Thyroid Hormone Replacement for Subclinical Hypothyroidism

NCT01660126Phase 4COMPLETED
Sponsor

NHS Greater Glasgow and Clyde

Enrollment

737

Started

2014

Primary outcome

Thyroid-specific quality of life - Hypothyroid symptoms and Fatigue symptoms (co-primary outcomes)

Subclinical Hypothyroidism

Effects of L-thyroxine Replacement on Serum Lipid and Atherosclerosis in Hypothyroidism

NCT01848171Phase 4UNKNOWN
Sponsor

Shandong Provincial Hospital

Enrollment

700

Started

2013

Primary outcome

Rate of First cardiovascular disorder (CVD) Events, CVD Mortality and All-cause Mortality

HypothyroidismThyroid DiseasesEndocrine System Diseases

The TRUST Study - Depression Substudy

NCT01853579Phase 4COMPLETED
Sponsor

Insel Gruppe AG, University Hospital Bern

Enrollment

426

Started

2013

Primary outcome

Change from baseline in 15-items Geriatric Depression Scale

Subclinical HypothyroidismDepression

Levothyroxine Intervention in Pregnant Women with TSH (2.5 MIU/L-upper Limit of Reference Range) and Negative Thyroid Peroxidase Antibody

NCT06653907Phase 4NOT_YET_RECRUITING
Sponsor

Yang ZHANG

Enrollment

400

Started

2024

Primary outcome

Rate of fetal loss

Thyroid AbnormalitiesPregnant WomanPregnancy Outcomes

Effect of L-Thyroxine on Lipid Profiles and Atherosclerosis in Subclinical Hypothyroidism

NCT01831869Phase 4UNKNOWN
Sponsor

Shandong Provincial Hospital

Enrollment

400

Started

2013

Primary outcome

change in lipid profile

HypothyroidismThyroid DiseasesEndocrine System Diseases

Effect of Thyroid Hormone Replacement on Fatigability in Untreated Older Adults With Subclinical Hypothyroidism

NCT02500342Phase 4COMPLETED
Sponsor

Insel Gruppe AG, University Hospital Bern

Enrollment

276

Started

2014

Primary outcome

Change from baseline in level of physical and mental fatigue as assessed by the Pittsburgh Fatigability Scale (PFS) score

Thyroid DysfunctionMental FatigueFatigue

Dosing of LT4 in Older Individuals

NCT06073665Phase 4RECRUITING
Sponsor

University of Pennsylvania

Enrollment

228

Started

2024

Primary outcome

Thyroid-Related Quality of Life Patient-Reported Outcome Quality of Life scale

Hypothyroidism

The TRUST Trial - CardioVascular Imaging ECHO

NCT02832960Phase 4COMPLETED
Sponsor

Insel Gruppe AG, University Hospital Bern

Enrollment

185

Started

2016

Primary outcome

Diastolic cardiac Function as measured by echocardiography

Thyroid DysfunctionAtherosclerosisHeart Failure

The TRUST Study - CardioVascular Imaging IMT

NCT02832934Phase 4COMPLETED
Sponsor

Insel Gruppe AG, University Hospital Bern

Enrollment

184

Started

2016

Primary outcome

Carotid Intima Media Thickness as measured by carotid ultrasound

Thyroid DysfunctionAtherosclerosisHeart Failure

Neurocognitive and Metabolic Effects of Mild Hypothyroidism

NCT00565864Phase 4COMPLETED
Sponsor

Oregon Health and Science University

Enrollment

173

Started

2008

Primary outcome

Executive Function

Hypothyroidism

Novel Biomarkers and Skeletal Outcomes Associated With Subclinical Thyroid Dysfunction

NCT02491008Phase 4COMPLETED
Sponsor

Insel Gruppe AG, University Hospital Bern

Enrollment

145

Started

2014

Primary outcome

Change in bone mineral density (BMD)

Thyroid DysfunctionBone Mineral DensityOsteoporosisFractures, Bone

Impact of Increasing Levothyroxine Dose in Ramadan for UAE Patients With Hypothyroidism

NCT06135948Phase 4COMPLETED
Sponsor

Emirates Health Services (EHS)

Enrollment

103

Started

2022

Primary outcome

Effects of an extra dose of L-thyroxine during the month of Ramadan

L-thyroxine

Low Dose Euthyrox in Treatments of Paraquat Intoxication.

NCT04132622Phase 4UNKNOWN
Sponsor

Second Affiliated Hospital, Zhejiang University, School of Medicine

Enrollment

80

Started

2020

Primary outcome

Rate of death weekly

Paraquat Poisoning

Bioequivalence Study of Levothyroxine Sodium Tablets 100 mcg

NCT04573907Phase 4COMPLETED
Sponsor

Tecnoquimicas

Enrollment

80

Started

2019

Primary outcome

(AUC) Area Under the Curve 0-48 for T4

Healthy

Randomized Crossover Trial for the Evaluation of the Possible Effects in the Intestine of Two Different Pharmaceutical Forms of L - Thyroxine in Patients With Primary Acquired Hypothyroidism

NCT02917863Phase 4UNKNOWN
Sponsor

Meyer Children's Hospital IRCCS

Enrollment

70

Started

2016

Primary outcome

Effects on gut inflammation parameter (Calprotectin)

Hypothyroidism

Levothyroxine Sodium in Thyroidectomized Patients Taking Proton Pump Inhibitors

NCT03094416Phase 4COMPLETED
Sponsor

IBSA Institut Biochimique SA

Enrollment

66

Started

2018

Primary outcome

Thyroid Stimulating Hormone (TSH)

Hypothyroidism;Postablative

Discontinuation of Levothyroxine Therapy for Patients With Subclinical Hypothyroidism

NCT04288115Phase 4COMPLETED
Sponsor

VA Office of Research and Development

Enrollment

52

Started

2021

Primary outcome

Participants' Willingness to Enter the Trial

Subclinical Hypothyroidism

Type 2 Deiodinase Gene Polymorphism and the Treatment of Hypothyroidism Caused by Thyroidectomy in Thyroid Cancer Patients.

NCT05247476Phase 4UNKNOWN
Sponsor

Zhongshan Hospital Xiamen University

Enrollment

50

Started

2021

Primary outcome

TSH suppression

Thyroid Cancer, PapillaryHypothyroidism

Study of Optimal Replacement of Thyroxine in the Elderly

NCT01647750Phase 4COMPLETED
Sponsor

Newcastle-upon-Tyne Hospitals NHS Trust

Enrollment

48

Started

2012

Primary outcome

Participant's acceptability of study design and willingness to enter study

Hypothyroidism

Use of Tirosint®-SOL or Tablet Formulations of Levothyroxine in Pediatric Patients With Congenital Hypothyroidism (CH)

NCT05228184Phase 4TERMINATED
Sponsor

IBSA Institut Biochimique SA

Enrollment

34

Started

2022

Primary outcome

LT4 Dose Required to Maintain TSH in Target Range (Unit: mcg/kg/Day)

Congenital Hypothyroidism

Thyroid Replacement Therapy in Patients With Subclinical Hypothyroidism

NCT04953195Phase 4UNKNOWN
Sponsor

Beijing Chao Yang Hospital

Enrollment

30

Started

2019

Primary outcome

Thyroid Stimulating Hormone changes

Subclinical Hypothyroidisms

Bioequivalence of Two Levothyroxine Tablet Formulations in Healthy Indian Volunteers

NCT01536678Phase 4COMPLETED
Sponsor

GlaxoSmithKline

Enrollment

26

Started

2012

Primary outcome

Maximum observed concentration (Cmax) and Area under concentration-time curve [AUC (0-48)]

Hypothyroidism

Thyroid Study Type 2 Diabetes Mellitus (T2DM)

NCT01379170Phase 4UNKNOWN
Sponsor

Maastricht University Medical Center

Enrollment

17

Started

2011

Primary outcome

Thyroid hormone-induced change in whole body insulin sensitivity (change in insulin-stimulated glucose disposal) and muscle mitochondrial function

DiabetesHypothyroidism

Evaluation of the Efficacy and Safety of Levothyroxine in Brain Death Organ Donors: a Randomized Controled Trial

NCT02211053Phase 4TERMINATED
Sponsor

Centre Integre Universitaire de Sante et Services Sociaux du Nord de l'ile de Montreal

Enrollment

15

Started

2014

Primary outcome

Study feasibility

Brain Dead Organ Donors

Levothyroxine Replacement With Liquid Gel Capsules vs Tablets Post-thyroidectomy

NCT02946918Phase 4TERMINATED
Sponsor

University of Texas Southwestern Medical Center

Enrollment

14

Started

2017

Primary outcome

Number of Patients in Each Group at Predefined Target TSH Range at 18 Weeks

Thyroid CancerPostsurgical Hypothyroidism

Use of Liquid Stable Levothyroxine in Trisomy 21 Pediatric Patients

NCT04747275Phase 4TERMINATED
Sponsor

Children's Mercy Hospital Kansas City

Enrollment

6

Started

2021

Primary outcome

Tolerability as Assessed by the CareCAT Tool

HypothyroidismTrisomy 21

Comparison of Levothyroxine Formulation in Hypothyroid Patients With Enteral Feeding

NCT04878614Phase 4TERMINATED
Sponsor

University of California, Los Angeles

Enrollment

3

Started

2021

Primary outcome

Change of TSH

Hypothyroidism

Thyroid Therapy for Mild Thyroid Deficiency in Pregnancy

NCT00388297Phase 3COMPLETED
Sponsor

The George Washington University Biostatistics Center

Enrollment

1,203

Started

2006

Primary outcome

Intellectual Function of Children at 5 Years of Age in Women Diagnosed With a) Subclinical Hypothyroidism or b) Hypothyroxinemia During the First Half of Pregnancy, or Death.

Subclinical HypothyroidismHypothyroxinemiaPregnancy

Levothyroxine as Adjuvant to a Hypocaloric Diet for the Treatment of Obesity.

NCT07332273Phase 3RECRUITING
Sponsor

Fundación Pública Andaluza para la Investigación de Málaga en Biomedicina y Salud

Enrollment

286

Started

2025

Primary outcome

Change in body weight (kg) from baseline to Month 3

Obesity

Thyroxin Treatment in Sub Clinical Hypothyroidism, on the Apnea Hypopnea Index Score, Lipids and Highly Sensitive CRP

NCT01486667Phase 3UNKNOWN
Sponsor

King Saud University

Enrollment

200

Started

2011

Primary outcome

Effect of the treatment of subclinical hypothyroidism on the apnea hypopnea index (AHI) score.

Dyslipidemia

Role of Levothyroxine Supplementation in Delayed Recovery Following Cardiac Surgery

NCT06660823Phase 3COMPLETED
Sponsor

Ain Shams University

Enrollment

70

Started

2024

Primary outcome

Change in Glasgow Coma Scale (GCS) From Intervention Initiation to ICU Discharge (Δ)

Cardiac Surgery Intensive Care TreatmentDelayed Recovery From AnaesthesiaEuthyroid Sick SyndromeCardiac Surgery Requiring Cardiopulmonary Bypass

TSH Suppression During Radiotherapy on Thyroid Site to Prevent Iatrogenic Hypothyroidism in Pediatric Cancer Patients

NCT05316922Phase 3RECRUITING
Sponsor

Fondazione IRCCS Istituto Nazionale dei Tumori, Milano

Enrollment

68

Started

2021

Primary outcome

Hypothyroidism-free survival

Hypothyroidism; Irradiation

L-Thyroxine Supplementation for Preterm Newborns Less Than 32 Weeks of Gestation With Hypothyroxinemia

NCT01306227Phase 3COMPLETED
Sponsor

Centre Hospitalier Universitaire, Amiens

Enrollment

50

Started

2006

Primary outcome

Neurodevelopmental outcome

Hypothyroxinemia

Supplementation of Thyroid Hormone for TSH Control in Patients With Chronic Kidney Disease Without TRR.

NCT03898622Phase 3COMPLETED
Sponsor

Hospital Civil de Guadalajara

Enrollment

32

Started

2018

Primary outcome

24 hours urine Proteinuria in patients with subclinical hypothyroidism and CKD G2-G5 without renal support therapy Randomized clinical trial of levothyroxine group versus placebo

Chronic Kidney DiseasesSubclinical Hypothyroidism

Novel Approaches to the Treatment of Hypothyroidism

NCT06731764Phase 2/3RECRUITING
Sponsor

UConn Health

Enrollment

90

Started

2024

Primary outcome

Changes in Total Cholesterol

Hypothyroidism

Subclinical Hypothyroidism and Mind in the Elderly

NCT00921050Phase 2/3COMPLETED
Sponsor

Universidad Autonoma de Nuevo Leon

Enrollment

70

Started

2009

Primary outcome

Change in cognitive ability measured by NEUROPSI increase of 10 points

Subclinical Hypothyroidism

Early Levothyroxine Post Radioactive Iodine

NCT01950260Phase 2/3COMPLETED
Sponsor

Mayo Clinic

Enrollment

61

Started

2013

Primary outcome

Number of Participants With Overt Hypothyroidism

Graves' Disease

Effects of Levothyroxine on Endothelial Function of Patients With Subclinical Hypothyroidism

NCT02090907Phase 2/3COMPLETED
Sponsor

Isfahan University of Medical Sciences

Enrollment

50

Started

2013

Primary outcome

Change from baseline flow-mediated dilation at 2 months

Subclinical Hypothyroidism

A Study Evaluating the Safety and Efficacy of Hormone Replacement Therapy With ST-1891 Compared to Levothyroxine in Patients With Primary Hypothyroidism

NCT05412979Phase 2COMPLETED
Sponsor

Sention Therapeutics, LLC

Enrollment

490

Started

2022

Primary outcome

Levothyroxine-to-ST-1891 dosing conversion factor

Hypothyroidism

A Study Evaluation the Safety and Efficacy of Hormone Replacement Therapy With North Star Compared to Levothyroxine in Patients With Primary Hypothyroidism

NCT05712421Phase 2COMPLETED
Sponsor

Neuvosyn Laboratories, LLC

Enrollment

303

Started

2023

Primary outcome

The ratio of the LT4 dose (mcg/day) at screening to North Star (mg/day) at the end of the treatment period required to achieve and maintain serum thyroid-stimulating hormone (TSH) levels within the normal reference range.

Hypothyroidism

A Study of Armour® Thyroid Compared to Synthetic T4 (Levothyroxine) in Previously Hypothyroid Participants

NCT04124705Phase 2COMPLETED
Sponsor

Allergan

Enrollment

284

Started

2019

Primary outcome

Percentage of Participants With a Sustained TSH Response

HypothyroidismThyroid DiseaseEuthyroidThyroid GlandThyroid Hormones

Study of Dose Adjustment From Levothyroxine to a New Levothyroxine Sodium Test Formulation

NCT01916304Phase 2COMPLETED
Sponsor

Takeda

Enrollment

101

Started

2013

Primary outcome

Percentage of Participants That Do Not Need a Change of Dose

Hypothyroidism

T4/T3 Therapy in Hypothyroidism

NCT07424183Phase 2NOT_YET_RECRUITING
Sponsor

University of Pennsylvania

Enrollment

60

Started

2026

Primary outcome

ThyPRO Composite QOL Scale

Hypothyroidism Primary

Study of XP-8121 For the Treatment of Adult Subjects With Hypothyroidism

NCT05823012Phase 2COMPLETED
Sponsor

Xeris Pharmaceuticals

Enrollment

46

Started

2023

Primary outcome

Dose Conversion Factor

Hypothyroidism

Levothyroxine for Non-Alcoholic Fatty Liver Disease (NAFLD)

NCT03281083Phase 2TERMINATED
Sponsor

Duke-NUS Graduate Medical School

Enrollment

29

Started

2014

Primary outcome

Liver fat content

Non-Alcoholic Fatty Liver DiseaseDiabetes Mellitus, Type 2

Thyroid and Glucose and Energy Metabolism

NCT00106119Phase 2COMPLETED
Sponsor

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Enrollment

18

Started

2005

Primary outcome

Insulin-mediated Glucose Disposal Rate at Levothyroxine Treatment Phase

Thyroid Diseases

Energy Metabolism in Thyroidectomized Patients

NCT04782856Phase 2COMPLETED
Sponsor

Virginia Commonwealth University

Enrollment

13

Started

2020

Primary outcome

Short Term Change in Weight

Thyroid GoiterHypothyroidismThyroid Cancer

Can Levothyroxine Treatment Reduce the Development of Cardio-metabolic Disorder in Subclinical Hypothyroidism?

NCT04178928Phase 1/2UNKNOWN
Sponsor

Ain Shams University

Enrollment

40

Started

2020

Primary outcome

: Normalization of TSH.

Subclinical hypothyroïdism

Levothyroxine Supplementation for Heart Transplant Recipients

NCT06428097Phase 1RECRUITING
Sponsor

University of California, San Francisco

Enrollment

97

Started

2024

Primary outcome

Number of participants who receive Levothyroxine's vasopressor use compared to number of participants who receive normal saline's vasopressor use.

Heart Transplant FailureHeart Transplant Infection

Study to Evaluate the Effect of IW-3718 on the Pharmacokinetics of Oral Contraceptive, Levothyroxine, Glyburide, and Digoxin in Healthy Adult Volunteers

NCT03856970Phase 1COMPLETED
Sponsor

Ironwood Pharmaceuticals, Inc.

Enrollment

87

Started

2019

Primary outcome

PK of EE and NET: Area Under the Plasma Concentration Versus Time Curve (AUC) From Time 0 to the Last Quantifiable Concentration (AUC0-t)

Healthy Volunteers

Compare Safety and Pharmacokinetic Properties of Surfolase Capsule(Acebrophylline 100mg) and Surfolase CR(200mg)

NCT02395913Phase 1COMPLETED
Sponsor

Hyundai Pharmaceutical Co., LTD.

Enrollment

72

Started

2013

Primary outcome

AUCt of ambroxol

Healthy Male

Bioequivalence of Two Formulations of Levothyroxine Sodium 200 Micrograms (mcg) Under Tablet Form

NCT04037748Phase 1COMPLETED
Sponsor

Merck Healthcare KGaA, Darmstadt, Germany, an affiliate of Merck KGaA, Darmstadt, Germany

Enrollment

72

Started

2019

Primary outcome

Baseline Corrected Maximum Observed Plasma Concentration (Cmax[Adj]) of Levothyroxine Sodium

Healthy

A Trial Investigating the Influence of Oral Semaglutide on the Pharmacokinetics of Levothyroxine and the Influence of Co-administered Tablets on the Pharmacokinetics of Semaglutide Administered Orally in Healthy Subjects.

NCT02920385Phase 1COMPLETED
Sponsor

Novo Nordisk A/S

Enrollment

45

Started

2016

Primary outcome

Baseline-corrected area under the total T4 serum concentration-time curve from 0 to 48 hours after a single dose of levothyroxine

DiabetesHealthy

Fasting Study of Levothyroxine Sodium Tablets 300 mcg to Synthroid® Tablets 300 mcg

NCT00648882Phase 1COMPLETED
Sponsor

Mylan Pharmaceuticals Inc

Enrollment

33

Started

2007

Primary outcome

Bioequivalence

Healthy

Fasting Study of Levothyroxine Sodium Tablets 200 mg to Synthroid Tablets 200 mg

NCT00648557Phase 1COMPLETED
Sponsor

Mylan Pharmaceuticals Inc

Enrollment

32

Started

2003

Primary outcome

Bioequivalence

Healthy

Fasting Study of Levothyroxine Sodium Tablets 300 μg to Levothroid® Tablets 300 μg

NCT00648700Phase 1COMPLETED
Sponsor

Mylan Pharmaceuticals Inc

Enrollment

32

Started

2005

Primary outcome

Bioequivalence

Healthy

A Study of Levothyroxine and Enlicitide Decanoate (MK-0616) in Healthy Adult Participants (MK-0616-028)

NCT06625814Phase 1COMPLETED
Sponsor

Merck Sharp & Dohme LLC

Enrollment

28

Started

2024

Primary outcome

Area under the Concentration-Time Curve from Time 0 to 48 hours (AUC0-48hrs) of Levothyroxine (total T4)

Healthy

Sorafenib Drug Drug Interaction Study in Healthy Male Subjects

NCT02332031Phase 1COMPLETED
Sponsor

Bayer

Enrollment

25

Started

2015

Primary outcome

Area under the concentration vs. time curve from zero to infinity after single (first) dose (AUC) of sorafenib

Drug Interactions

Bioavailability Investigations of Thyronajod Mite Tablets of Dosage Strengths 50 μg Levothyrox-ine/75 μg Iodine, and 100 μg Levothyroxine/75 μg Iodine vs. a Levothyroxine Drinking-Solution: A Randomised Cross Over Study in Healthy Male Individuals. Currently: 50 μg/ 75 μg Tablets

NCT01465633Phase 1COMPLETED
Sponsor

Heidelberg University

Enrollment

24

Started

2003

Pharmacokinetics

Bioavailability Investigations of Thyronajod Mite Tablets of Dosage Strengths 50 μg Levothyrox-ine/75 μg Iodine, and 100 μg Levothyroxine/75 μg Iodine vs. a Levothyroxine Drinking-Solution: A Randomised Cross Over Study in Healthy Male Individuals. Currently: 100 μg/ 75 μg Tablets

NCT01465646Phase 1COMPLETED
Sponsor

Heidelberg University

Enrollment

24

Started

2003

Pharmacokinetics

Recurrent Pregnancy Loss and Thyroid Disease

NCT03106935Early Phase 1UNKNOWN
Sponsor

Second Affiliated Hospital of Soochow University

Enrollment

300

Started

2015

Primary outcome

Gestational week at delivery

Recurrent Pregnancy Loss

A Clinical Trial of Adjunctive Thyroxine for Avolition in Schizophrenia

NCT07011953Early Phase 1NOT_YET_RECRUITING
Sponsor

Peking University

Enrollment

90

Started

2025

Primary outcome

the score of Motivation subscale of the Negative Symptom Assessment (NSA-15)

SchizophreniaAvolition

MASLD in Primary Hypothyroidism and Efficacy of Dapaglifozin

NCT06373523Early Phase 1ACTIVE_NOT_RECRUITING
Sponsor

Post Graduate Institute of Medical Education and Research, Chandigarh

Enrollment

50

Started

2024

Primary outcome

Change in liver fat content

Hepatic Steato-FibrosisNon-Alcoholic Fatty Liver Disease

Effect of Age, Weight and Sex on Levothyroxine Pharmacokinetics

NCT03102177Early Phase 1COMPLETED
Sponsor

Georgetown University

Enrollment

41

Started

2011

Primary outcome

CL/F

Hypothyroidism Primary

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