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Study on Levothyroxine and Low-Calorie Diet for Weight Loss in Obese Patients with Subclinical Hypothyroidism or High-Normal TSH Levels

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying the effects of a medication called levothyroxine sodium in combination with a low-calorie diet and exercise recommendations for the treatment of obesity. The study is particularly interested in individuals who have obesity along with a condition known as subclinical hypothyroidism, which is a mild form of underactive thyroid, or those who have normal thyroid function but with thyroid-stimulating hormone (TSH) levels at the higher end of the normal range. The trial will compare the effects of levothyroxine sodium with a placebo, which is a substance with no active medication, to see how it impacts weight loss and body composition over a period of three months.

Participants in the study will follow a specific lifestyle strategy that includes a low-calorie diet and physical activity. The main goal is to observe changes in weight and body composition, such as body mass index (BMI), waist and hip measurements, and fat mass. The study will also look at other health factors, including cardiovascular risk factors like blood pressure and cholesterol levels, as well as changes in energy expenditure and physical activity levels. Additionally, the study will explore how these treatments affect heart function, metabolic activity, and overall quality of life.

The trial aims to provide insights into whether adding levothyroxine sodium to a lifestyle intervention can enhance weight loss and improve health outcomes in people with obesity and specific thyroid conditions. The study will last for several months, with the primary focus on the first three months, and will continue to monitor participants to assess the long-term effects of the treatment. The findings could help in understanding the role of thyroid hormones in weight management and potentially offer new strategies for treating obesity.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, participants are required to provide informed consent. This is a formal agreement to participate after understanding the study's purpose and procedures.

  2. Step 2

    Initial assessment

    Participants undergo an initial assessment to record baseline measurements. This includes weight, body composition, and other health indicators such as blood pressure and glucose levels.

  3. Step 3

    Medication administration

    Participants are randomly assigned to receive either levothyroxine sodium or a placebo. The medication is administered orally in the form of a tablet called Eutirox 88 microgramos comprimidos.

    The dosage and frequency of administration are determined by the study protocol and are consistent throughout the trial.

  4. Step 4

    Diet and exercise regimen

    Participants follow a hypocaloric diet, which is a diet with reduced calorie intake, along with physical exercise recommendations. This lifestyle strategy is maintained for the duration of the trial.

  5. Step 5

    Ongoing monitoring

    Throughout the trial, participants are monitored for changes in weight, body composition, and other health parameters. This includes regular check-ups and assessments to track progress and any side effects.

  6. Step 6

    Final assessment

    At the end of the 3-month intervention period, a final assessment is conducted. This includes measuring weight loss, body composition changes, and other health indicators to evaluate the effectiveness of the treatment.

  7. Step 7

    Follow-up period

    After the initial 3-month period, participants enter a follow-up phase to monitor weight regain prevention and other long-term health outcomes. This phase continues until the end of the study.

Who can join the trial?

4 criteria

  • Participants must be between 25 and 60 years old.
  • Participants should have **Grade I-II obesity**, which means a **Body Mass Index (BMI)** between 30 and 39.9. BMI is a number calculated from a person's weight and height.
  • Participants can have **subclinical hypothyroidism**, which means their **Thyroid Stimulating Hormone (TSH)** levels are between 5 and 10, but other thyroid hormones are normal. Alternatively, they can be **euthyroid**, meaning their thyroid is functioning normally, but their TSH levels are in the higher range of normal for people without thyroid disease.
  • Participants must agree to join the study by providing **informed consent**, which means they understand the study and agree to participate.

Who cannot join the trial?

4 criteria

  • Individuals with any **metabolic disease**. A metabolic disease affects how your body processes food and energy.
  • People who are not within the specified age range for the study.
  • Participants who do not have obesity or specific thyroid conditions, such as **subclinical hypothyroidism** or **euthyroidism** with high-normal **TSH levels**. Subclinical hypothyroidism means your thyroid is underactive but not showing obvious symptoms. Euthyroidism means your thyroid is functioning normally. TSH is a hormone that helps control your thyroid.
  • Individuals who are part of a vulnerable population, which means they might need special protection or care.
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Investigated drugs

Levothyroxine is a medication used in this trial as an additional treatment to help with weight loss. It is being tested to see if it can improve the effects of a low-calorie diet and exercise in people who are obese and have either mild thyroid issues or normal thyroid function with slightly higher thyroid-stimulating hormone (TSH) levels. The goal is to see if adding levothyroxine can help these individuals lose more weight and improve their body composition over three months.

What is already known about the treatment

Levothyroxine – Levothyroxine is administered orally in tablet form and is used as an adjuvant therapy in combination with a hypocaloric diet and physical exercise to aid weight loss in individuals with obesity and subclinical hypothyroidism or euthyroidism. It is currently being studied in clinical trials to assess its effectiveness in this context. The main therapeutic indication is for metabolic diseases, particularly in managing obesity when thyroid hormone levels are not optimal. Levothyroxine works by supplementing the body's natural thyroid hormone, which helps regulate metabolism and energy use. It is classified as a thyroid hormone replacement therapy.

Investigated diseases

  • Obesity

    Obesity is a condition characterized by excessive body fat accumulation that may impair health. It typically develops when calorie intake exceeds calorie expenditure over time, leading to weight gain. Obesity is often measured using the Body Mass Index (BMI), with a BMI of 30 or higher indicating obesity. The condition can progress to more severe forms, such as obesity type I and II, based on increasing BMI levels. Obesity is associated with various health risks, including cardiovascular diseases and metabolic disorders. Lifestyle factors, such as diet and physical activity, play a significant role in its development and progression.

  • Subclinical Hypothyroidism

    Subclinical hypothyroidism is a condition where the thyroid gland does not produce enough hormones, but the deficiency is not severe enough to cause obvious symptoms. It is often identified by elevated levels of Thyroid Stimulating Hormone (TSH) with normal levels of thyroid hormones in the blood. This condition can progress slowly and may remain stable for years without causing significant health issues. However, it can sometimes lead to overt hypothyroidism, where symptoms become more apparent. Subclinical hypothyroidism is more common in women and older adults. Regular monitoring of thyroid function is often recommended to track any changes in hormone levels.

Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-514377-22-00Protocol codeLEVOBESITYEstimated enrolment286 patientsSponsorFundacion Publica Andaluza Para La Investigacion De Malaga En Biomedicina Y Salud

sourced from the EU Clinical Trials Register and site verification

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