About Testosterone

Testosterone is the major male sex hormone.

Testosterone is produced in the testicles. It causes masculinising changes seen at puberty and maintains the maleness and sexuality of men.

What happens to testosterone?

Man may have 7 ages but there are only 3 ages of testosterone output. Pre-puberty there is little then it surges to cause puberty and to create the essential male features at the start of the second age. In the 30s and 40s testosterone is very present and ‘maleness’ very recognizable.

Look around a group of men in their 70’s, however, and you can see the third age- some who have beard loss or skin thinning and identifiable loss of maleness both physically and mentally.

Another example of low testosterone in an adult is the eunuch. We know that a eunuch has no testicles and consequently low testosterone. He has no beard, gets fat, is likely to have shrinking of the penis and often will be impotent and thus be no danger to the ladies of the harem. In essence this is the effect of falling testosterone with increased age, too.

These phenomena gradually occur in men as they get into their 60’s and 70’s and testosterone output falls.

The andropause?

All women have a menopause.

This is when the ovaries stop producing oestrogen and consequently the periods cease. Things are more variable in men– there is no acute cessation of testosterone production. So although journalists may talk of the andropause, a time when testosterone production ceases, in fact, there is a steady decline of testosterone output from the age of 40. How much this affects each individual depends on how much it drops off. The rate is between 0.5 and 2.5% per year.

What is the hormonal picture in men by age?

The chart below shows the range of Total Testosterone by age group. The groups are roughly 20’s, 40’s, 50’s, 70’s, and 80’s. There are 4 major studies shown here. At each age group there are 3 measurements shown: the mean (the middle of the range or if you like the average) and the low and high points of the Standard Deviation (the SD). The SD is a range that includes 90% of the population and shows “normality”.

You can see that the studies agree closely for each age group, that the range of values seen falls with increasing age and how many men are falling below 15 nmol/L for each group. Below 15 there is significant erectily dysfunction – failure to achieve or maintain an erection.

The andropause?

A blood test for testosterone should be taken in the morning. There is a variation across the day with a fall in the mid afternoon. Standardizing the timing allows for better comparisons within each person’s series of tests such as before and after treatment. There is no need to fast or modify your sexual behavior.

The next question is “there are several possible tests – what should we measure?”

We need to ask this question because of the way testosterone is carried around in the circulation and how this changes with age.

The answer is that the best test is the free testosterone (free T). This test shows the testosterone that is “free” in the plasma and available for the body to use.

As we age the free T falls faster than other measures and shows more precisely what is happening to the testosterone impact.

The other measurement commonly used is the total testosterone (Total T).

This is not as accurate a measure to base decisions on in older men but if it is low then there are definitely problems present.

For more information on how testosterone is carried around the body and why Free T is the best measurement see Testosterone transport in the blood stream.

Sexual function

In men mood problems may be the first sign of falling testosterone. Erection difficulty (ED) begins to appear in some men as early as their late 40’s if the blood level falls, significantly. Such problems occur at a blood level of between 10 and 12 nmol/L.

In older men, few 80 year olds can achieve intercourse. Overall the figures for problems are that around 40% of men in their 50s, 50% of men in their 60’s, and more than 50% in their 70’s, have low testosterone and diminished sexual function.

So it is true to say that men do not have acute event like every woman’s menopause, but that does not mean that there are no problems.

In fact: low testosterone is dangerous.

Men with low testosterone are at a greater risk of dying early than those with normal testosterone.