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Study on Levothyroxine and Sildenafil for Improving Erectile Function in Patients with Subclinical Hypothyroidism and Erectile Dysfunction

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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 two medications, levothyroxine and sildenafil, on individuals with hypothyroidism and erectile dysfunction. Hypothyroidism is a condition where the thyroid gland does not produce enough hormones, which can affect various bodily functions, including sexual health. Erectile dysfunction is the inability to achieve or maintain an erection suitable for sexual activity. Levothyroxine is a medication used to treat hypothyroidism by replacing the hormone that the thyroid gland is unable to produce. Sildenafil is commonly used to treat erectile dysfunction by increasing blood flow to the penis.

The purpose of this study is to assess how levothyroxine, when adjusted for weight and baseline thyroid-stimulating hormone (TSH) levels, impacts sexual activity in patients with subclinical hypothyroidism and erectile dysfunction. Participants will be randomly assigned to receive either levothyroxine, sildenafil, or a placebo. The study will last for three months, during which participants will take the medication orally. Throughout the study, participants will complete questionnaires to evaluate changes in their erectile function and overall satisfaction with the treatment.

Participants will be monitored at the beginning of the study and again after three months to track any changes in their condition. The study aims to provide insights into the effectiveness of levothyroxine in improving erectile function in patients with subclinical hypothyroidism. This research could potentially lead to better treatment options for individuals experiencing these conditions.

The research process

The trial runs in 5 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, eligibility is confirmed based on specific criteria. Participants must be heterosexual males over 18 years, sexually active, diagnosed with subclinical hypothyroidism (TSH >5 with normal T4), and have erectile dysfunction as per the IIEF-15 questionnaire (score <25 points).

    Participants must be able to complete the IIEF-15, EHS, PGIC, and EDITS questionnaires and provide informed consent.

  2. Step 2

    Baseline assessment

    Initial assessments are conducted to establish baseline measurements. This includes completing the IIEF-15, EHS, PGIC, and EDITS questionnaires to evaluate erectile function and satisfaction with treatment.

  3. Step 3

    Treatment phase

    Participants receive treatment with levothyroxine and sildenafil. Levothyroxine dosage is adjusted based on weight and baseline TSH values. Sildenafil is administered at a dose of 100 mg.

    Both medications are taken orally. The treatment aims to assess the impact on sexual activity and erectile function.

  4. Step 4

    Follow-up assessment

    After three months of treatment, participants complete the IIEF-15, EHS, PGIC, and EDITS questionnaires again to evaluate changes in erectile function and treatment satisfaction.

    The evolution of scores from these questionnaires is analyzed to determine the effectiveness of the treatment.

  5. Step 5

    End of study

    The study is estimated to conclude by April 30, 2027. Participants' data will contribute to understanding the impact of levothyroxine on erectile function in patients with subclinical hypothyroidism.

Who can join the trial?

6 criteria

  • Must be a heterosexual male over 18 years old.
  • Must be sexually active.
  • Must have been diagnosed with subclinical hypothyroidism, which means having a thyroid-stimulating hormone (TSH) level greater than 5 with normal T4 levels. TSH and T4 are hormones related to thyroid function.
  • Must have a diagnosis of erectile dysfunction (ED) according to the International Index of Erectile Function (IIEF-15) questionnaire, with a score of less than 25 points. This questionnaire helps assess erectile function.
  • Must be able to complete the IIEF-15, Erectile Hardness Score (EHS), Patient Global Impression of Change (PGIC), and Erectile Dysfunction Inventory of Treatment Satisfaction (EDITS) questionnaires. These are tools used to measure different aspects of sexual health and satisfaction.
  • Must sign an informed consent, which means agreeing to participate in the study after being informed about all the details and implications.

Who cannot join the trial?

5 criteria

  • Patients who do not have **subclinical hypothyroidism**. This means their thyroid gland is not underactive, which is usually checked by a blood test showing a **TSH** (Thyroid Stimulating Hormone) level greater than 5.
  • Patients who do not have **erectile dysfunction**. This is a condition where a man has difficulty getting or keeping an erection.
  • Patients who are not male, as the study is only for male participants.
  • Patients who are not within the specified age range for the study.
  • Patients who belong to 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 to treat patients with subclinical hypothyroidism. It helps to regulate the thyroid hormone levels in the body, which can improve various bodily functions, including sexual activity. The trial aims to see how levothyroxine affects erectile function in patients with hypothyroidism.

  • Sildenafil

    is another medication used in this trial. It is commonly known for treating erectile dysfunction by increasing blood flow to the penis, which helps achieve and maintain an erection. In this study, sildenafil is used to compare its effects on erectile function with those of levothyroxine in patients with hypothyroidism.

What is already known about the treatment

Levothyroxine – Levothyroxine is administered orally in tablet form and is primarily used to treat hypothyroidism, a condition where the thyroid gland does not produce enough hormones. It is currently well-established in medical practice and literature as a standard treatment for thyroid hormone replacement. The main therapeutic indication for levothyroxine is to restore normal hormone levels in patients with hypothyroidism, including subclinical cases. At the molecular level, levothyroxine works by replacing or supplementing the thyroid hormone, thereby regulating the body's energy and metabolism. It is classified pharmacologically as a thyroid hormone replacement therapy.

Investigated diseases

  • Subclinical Hypothyroidism

    This condition occurs when the thyroid gland does not produce enough hormones, but the deficiency is not severe enough to cause obvious symptoms. It is characterized by an elevated level of thyroid-stimulating hormone (TSH) while the levels of thyroid hormones (T3 and T4) remain normal. People with subclinical hypothyroidism may experience mild symptoms such as fatigue, weight gain, or feeling cold. Over time, if untreated, it can progress to overt hypothyroidism, where symptoms become more pronounced. The condition is often detected through routine blood tests rather than noticeable symptoms. Monitoring and regular check-ups are important to manage the condition effectively.

  • Erectile Dysfunction

    This condition is characterized by the inability to achieve or maintain an erection sufficient for satisfactory sexual performance. It can result from physical causes such as heart disease, diabetes, or hormonal imbalances, as well as psychological factors like stress or anxiety. The condition can affect men of all ages but is more common as men get older. Erectile dysfunction can lead to reduced self-esteem and stress in relationships. It often progresses gradually, with symptoms worsening over time if underlying causes are not addressed. Lifestyle changes and addressing underlying health issues can help manage the condition.

Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-514789-38-00Protocol code457531Estimated enrolment90 patientsSponsorAsociacion Instituto De Investigacion Sanitaria Biobizkaia

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