Underactive Thyroid and Erectile Dysfunction

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How does underactive thyroid and erectile dysfunction connect?

An underactive thyroid (hypothyroidism) slows down many body processes, including those needed for healthy erections [1]. Thyroid hormones help regulate metabolism, energy production, and blood vessel function—all essential for sexual arousal and maintaining an erection.

Men with untreated hypothyroidism often experience reduced libido, fatigue, and difficulty achieving or keeping an erection [2]. The thyroid gland produces hormones that influence testosterone levels; when thyroid function is low, testosterone production may also drop, further contributing to erectile dysfunction.

Hypothyroidism can also affect the nervous system and blood circulation, both critical for the physical process of erection. Additionally, the condition commonly causes depression and low mood, which are themselves risk factors for ED [1]. The good news is that many of these effects are reversible once thyroid hormone levels are restored to normal with appropriate treatment.

What causes erectile dysfunction in men with hypothyroidism?

Several mechanisms link thyroid problems to erection difficulties. Low thyroid hormone levels reduce the activity of enzymes needed to produce nitric oxide, a molecule that relaxes blood vessels in the penis and allows blood to flow in during arousal [2]. Without sufficient nitric oxide, achieving a firm erection becomes difficult.

Hypothyroidism also disrupts the balance of sex hormones. Thyroid hormones help regulate sex hormone-binding globulin (SHBG), a protein that carries testosterone in the blood. When thyroid function is low, SHBG levels can rise, reducing the amount of free (active) testosterone available [10]. Lower testosterone contributes to reduced sexual desire and weaker erections.

Fatigue and weight gain—common symptoms of an underactive thyroid—can further worsen erectile function. Excess weight, particularly around the abdomen, is associated with reduced testosterone and poorer blood vessel health. Depression and low self-esteem, which often accompany hypothyroidism, create additional psychological barriers to sexual performance [1]. Addressing the underlying thyroid condition is therefore a crucial first step in managing ED.

Does levothyroxine help erectile dysfunction?

Levothyroxine, the standard treatment for hypothyroidism, replaces the missing thyroid hormone and can significantly improve erectile function in many men [2]. Studies show that once thyroid levels normalise, testosterone often rises, energy returns, and blood vessel function improves—all of which support better erections.

However, improvement may take several weeks or months as the body adjusts to stable thyroid hormone levels. Some men find that ED resolves completely with thyroid treatment alone, while others benefit from additional ED medication once their thyroid condition is well controlled. It is important to have regular blood tests to ensure your levothyroxine dose is correct, as both under- and over-treatment can affect sexual function.

When to get urgent help

• Erection lasting more than 4 hours (priapism)—go to A&E immediately
• Sudden loss of vision or hearing after taking ED medication—seek urgent medical help
• Chest pain during or after sex—call 999
• Severe dizziness or fainting after taking ED medication—seek immediate medical advice
• New or worsening ED alongside chest pain, breathlessness, or fatigue—see your GP urgently to rule out heart disease

Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.

How is underactive thyroid and erectile dysfunction assessed?

If you have both thyroid problems and erection difficulties, your GP will typically check your thyroid function with a blood test measuring thyroid-stimulating hormone (TSH) and free thyroxine (T4) [2]. If your thyroid is underactive, the priority is to optimise your levothyroxine dose before considering other treatments for ED.

Your doctor may also check testosterone levels, as low testosterone is common in men with hypothyroidism and can independently cause erectile dysfunction [10]. Other blood tests—such as glucose, cholesterol, and kidney function—help identify additional risk factors like diabetes or cardiovascular disease, which often coexist with thyroid disorders.

A full medical history is essential: your GP will ask about the timing of your symptoms, any other health conditions, medications you take, and lifestyle factors such as smoking, alcohol, stress, and relationship issues [1]. This holistic assessment ensures that all contributing factors are addressed. If your thyroid levels are well controlled but ED persists, your doctor may refer you to a specialist or discuss ED medication options.

What lifestyle changes help with underactive thyroid and erectile dysfunction?

Even with medication, lifestyle measures play an important role in managing both hypothyroidism and erectile dysfunction. Maintaining a healthy weight is particularly beneficial: losing excess body fat can improve thyroid hormone metabolism, raise testosterone levels, and enhance blood vessel function [1][2].

Regular physical activity—at least 150 minutes of moderate exercise per week—boosts energy, improves mood, and supports cardiovascular health, all of which contribute to better erections [1]. Exercise also helps counteract the fatigue and weight gain associated with an underactive thyroid.

A balanced diet rich in fruits, vegetables, whole grains, and lean protein supports overall metabolic health. Limiting alcohol is important, as heavy drinking worsens both thyroid function and erectile performance [1]. If you smoke, stopping is one of the most effective steps you can take: smoking damages blood vessels and significantly increases the risk of ED [1]. Managing stress through relaxation techniques, good sleep, and open communication with your partner can also make a meaningful difference to sexual confidence and function.

Can diet affect thyroid function and erections?

While diet alone cannot cure hypothyroidism, certain nutrients support thyroid health. Iodine and selenium are essential for thyroid hormone production, though most people in the UK get enough from a varied diet [2]. Excessive iodine supplements can interfere with thyroid medication, so discuss any supplements with your GP or pharmacist.

A diet that supports heart health—low in saturated fat and rich in omega-3 fatty acids—also benefits erectile function by improving blood flow. Avoiding excessive processed foods and sugar helps maintain a healthy weight and stable blood glucose, both important for sexual health [1].

At a glance

What ED treatments are safe for men with underactive thyroid and erectile dysfunction?

Once your thyroid levels are stable on levothyroxine, oral ED medications known as PDE5 inhibitors are generally safe and effective [2][3]. These include sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra), and avanafil (Spedra). They work by increasing blood flow to the penis when you are sexually aroused, helping you achieve and maintain an erection.

There are no known direct interactions between levothyroxine and PDE5 inhibitors, so men with well-controlled hypothyroidism can usually take ED medication without additional concerns [3][4][5][6]. However, it is essential to declare all your current medicines—including thyroid medication—during your consultation, as your prescriber will check for any other conditions or drugs that might affect suitability.

PDE5 inhibitors are not suitable for everyone: they must never be taken with nitrates (such as GTN spray), nicorandil, or recreational drugs called poppers, as this combination can cause a dangerous drop in blood pressure [3]. Men taking alpha-blockers for prostate symptoms or high blood pressure need careful dose adjustment [3]. Your prescriber will review your full medical history to ensure ED treatment is safe for you. All ED medications at Cured Pharmacy are prescription-only and supplied after an online consultation reviewed by a UK-registered prescriber.

Which ED medication should I choose if I have hypothyroidism?

The choice of ED medication depends on your preferences, how spontaneous you want to be, and how your body responds. Sildenafil (Viagra) is taken about an hour before sex and lasts around four to six hours [3]. It is available in 25mg, 50mg, and 100mg strengths, and is the most widely used and affordable option.

Tadalafil (Cialis) offers more flexibility: the on-demand dose (10mg or 20mg) can be taken at least 30 minutes before sex and its effect can last up to 36 hours, earning it the nickname 'the weekend pill' [4]. Tadalafil is also available as a low daily dose (2.5mg or 5mg), which means you do not need to plan ahead—you can be ready for sex at any time.

Vardenafil (Levitra) works similarly to sildenafil, taken 25–60 minutes before sex, and may be an alternative if sildenafil does not suit you [5]. Avanafil (Spedra) is the fastest-acting option, working in as little as 15–30 minutes, which some men prefer for spontaneity [6][11]. All these medicines require sexual stimulation to work—they do not cause an automatic erection. Your prescriber can help you choose the most suitable option based on your lifestyle, other medications, and any other health conditions.

Can I take ED medication long-term with thyroid treatment?

Yes, PDE5 inhibitors can be used long-term alongside levothyroxine, provided your thyroid levels remain stable and you have regular check-ups with your GP [2][3]. Many men with hypothyroidism find that a combination of optimised thyroid treatment and ED medication gives them the best results.

It is important to continue monitoring your thyroid function with blood tests as recommended by your doctor, as changes in your thyroid dose can affect your overall health and potentially your sexual function. If you notice any new symptoms or side effects, contact your GP or pharmacist for advice.

In summary

• Hypothyroidism can cause ED by lowering testosterone, reducing blood flow, and causing fatigue.
• Treating your underactive thyroid with levothyroxine often improves erectile function over time.
• ED medications like sildenafil and tadalafil are safe to use alongside thyroid treatment.
• Lifestyle changes—weight loss, exercise, stopping smoking—support both thyroid and sexual health.
• Always declare your thyroid medication during your ED consultation for a safe prescription.

Frequently Asked Questions