Thyroid and testosterone: how your thyroid affects your male hormones

Your libido has been lower for a while, your morning erections have faded, and you do not feel like the man you were a few years ago. Logical thought: my testosterone must be low. Often that is true, but sometimes testosterone is not the lead role, but the victim of something else, higher up.

Because your thyroid and your sex hormones are connected. A thyroid that is out of balance can quietly drag your testosterone and your sexual function along, without you noticing.

How are thyroid and testosterone connected?

Your thyroid hormone influences, among other things, a protein in your blood that binds testosterone, called SHBG. If your thyroid function shifts, the ratio between your bound and your free, usable testosterone can shift too.

On top of that, your whole hormone system works as a network. If one gland is out of balance, the others feel it. Your thyroid and your testes make different hormones, but they are part of the same larger whole.

What does an underactive thyroid do to your testosterone and libido?

With an underactive thyroid, doctors relatively often see symptoms around libido and erection. In research among men with an underactive thyroid, reduced interest in sex clearly occurs more often, and some of those symptoms can recover once the thyroid is well managed again.

That is an important insight. It means that if you fixate on your testosterone, you can miss the actual driver, your thyroid. The complaint is your libido, but the cause sometimes sits one floor up.

And an overactive thyroid?

An overactive thyroid can affect your sexual function too. In men with an overactive thyroid, symptoms such as premature ejaculation and erection problems occur, for example, which often improve as the thyroid calms down.

In other words: both too slow and too fast can disrupt your male function. If you want to grasp the underlying picture, first read our pillar thyroid health in men.

Which blood values do you test together?

Precisely because thyroid and testosterone are intertwined, it is useful not to look at them separately. A doctor can request a logical combination, so you do not turn one dial while the problem sits with the other.

The table below shows which values are often looked at together, and what they add.

You will also find these values individually, such as TSH and total testosterone. According to the NHG-Standaard Schildklieraandoeningen, it is wise to measure in a targeted way for persistent symptoms rather than guessing which hormone is the culprit.

What if your thyroid is fine but your testosterone stays low?

Sometimes your thyroid turns out to work fine, and your testosterone is still low. Then the cause lies elsewhere, and it is important not to keep dwelling on the thyroid. Low testosterone can have many different backgrounds.

Think of excess weight, poor sleep, chronic stress or ageing, which can all push your testosterone down. Here too: one low value is not a diagnosis, and a doctor will often suggest a repeat measurement in the morning.

In that case it pays to look more broadly at your lifestyle and your other blood values. That way you avoid treating a thyroid that is perfectly fine, while the real gain is to be found elsewhere.

Treat the thyroid or testosterone first?

If both seem out of balance, the order matters. Many doctors look at the thyroid first, because a well-managed thyroid can clear up the testosterone picture. Sometimes the testosterone then moves along on its own.

This is very much something to discuss with a doctor, because guessing the order yourself can put you on the wrong track. The Hormones Man panel maps your male hormones, and for the complete picture including your thyroid there is the Complete Men’s Health Panel. If you are unsure between burnout and a hormonal cause, our piece burnout or low testosterone helps.

Sources

1. NHG (Dutch College of General Practitioners). NHG-Standaard Schildklieraandoeningen.
2. Thuisarts.nl. I want to know more about my thyroid.

Disclaimer

Caliberhealth works with BIG-registered doctors who review your blood results. This article provides general information and is not a substitute for medical advice from a GP or specialist. A blood test is a tool, not a diagnosis in itself. For serious or persistent symptoms, contact your GP, or call 112 in an emergency.