Q&A: Prof Malcolm Carruthers

What is testosterone resistance?
This a situation where men—especially those over 50—suffer from symptoms associated with insufficient levels of testosterone being produced by the body. Testosterone resistance is when those symptoms are not caused by low testosterone levels, but by the body’s inability to process the testosterone it is producing effectively.

What is testosterone and why do we need it?
It is often labelled ‘the sex hormone’, because it is responsible for the sex drive and sexual function in men. But it is much more than that. It is responsible for energy, drive, the maintenance of many of the body’s systems. For example, it is the reason men tend to have bigger muscles and bigger bones than women.

What first sparked the idea that testosterone resistance might be an issue?
I kept seeing men in my practice who had all of the symptoms of low testosterone, but whose levels tested within the normal spectrum. There seemed to be no direct correlation between the level of the hormone and their symptoms. They were telling me that they were suffering from the same symptoms that their wives had when they hit the menopause.

What are the symptoms?
Loss of energy, loss of drive, loss of libido, loss of early morning erections is a classic sign, joint pain, night sweats. But it can also affect other areas like bone and muscle mass—testosterone plays a role in maintaining many bodily systems.

Many told me that the symptoms were devastating their lives, causing the collapse or sale of businesses as they lost their drive, a loss of sexual interest or function, or that they had slid into depression. They were suffering from relationship breakdowns and many other problems, yet there seemed to be no help out there for them.

Is it common?
I believe that testosterone deficiency is a far more common condition than is generally recognised. I think that around 20 per cent of men over the age of 50 suffer from it as opposed to two per cent, which is generally quoted. The reason the figures are so different is because they count two different things. The official figures only count men who show low testosterone levels after a blood test. This assumes that the hormone is working at full effectiveness. My estimate includes men who suffer from low production, but crucially includes that set of men who are producing what is deemed enough testosterone, but for some reason it is not performing properly. This is what I call ‘testosterone resistance’.

Is there resistance to the idea in wider medical circles?
Endocrinologists, who are the people who specialise in hormonal matters, believe you can diagnose testosterone deficiency simply by testing for levels of the hormone. I believe this is not the case. These clinicians also work with diabetes, which they don’t diagnose simply by measuring insulin. They accept that the body can develop a resistance to insulin present in the body and this is often the major factor in the development of type two diabetes. I think they should adopt the same approach towards testosterone.

Why is there resistance to the idea?
Like any hormone, too much testosterone can have negative effects such as thickening of the blood increasing the risk of blood clots, disturbed liver function, increased aggression and there has been talk of an increased risk of prostate cancer, but this is still a hypothesis which has not been supported by research to date.

But the thing to remember is that these are problems associated with high levels of testosterone activity in the system, and this is a very different thing from high levels. I believe I have shown that you can have high levels of testosterone in the body but low levels of activity because of testosterone resistance. In which case, treatment may be necessary to increase your testosterone levels.

Have you conducted research in the area?
Part of my training was in chemical pathology. I have done extensive research into the area of testosterone and laid out the evidence detailing the mechanisms at work as I see them. There is a protein in the blood which can bind to testosterone molecules and stop them from working, greatly reducing the effectiveness of the testosterone in the system. This binding process increases as you age, making it more of an issue for men over 50.

There are also testosterone receptors throughout the body that can become compromised for a series reasons, including illness or stress, the latter of which reduces the body’s ability to absorb the hormone. Also, you simply produce less testosterone as you age. So there are several factors at play, all of which can be demonstrated. It can be a bit frustrating when the ideas fall on deaf ears, but things slowly beginning to improve.

What treatment is available?
There are a range of testosterone preparations. Some are made using a natural testosterone molecule produced from soy plants which when tweaked a bit, becomes what we call bio-identical. This means it is the same as the molecules produced in the body and will react in the same way as the body’s own testosterone. There are other preparations that are wholly synthetic, and these can have extra side chains added to either make it more easily absorbed, or longer acting. I prefer the natural hormone, as it seems to work better and have less side effects. Also, it is easily absorbed through the skin via a paste, as opposed to the injections or pills that many of the synthetic testosterones necessitate.

When we find that a patient is suffering from testosterone resistance, we usually prescribe a daily dose of testosterone and patients are often aware of changes quite quickly—within a few weeks, symptoms that have plagued them for years start to disappear. Their energy, drive and libido begin to return and often they get in touch to say just how much the treatment has improved their lives. This is wonderful to hear and makes it a very satisfying treatment to be able to offer.

For more information, visit the Centre For Men’s Health