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Balance app founder Dr Louise Newson tackles the topic of testosterone
Testosterone is a really important hormone for women. It is the most biologically effective hormones working on every cell in your body and has important effects on your body and brain.
How do I know if my testosterone levels are low?
Levels of testosterone usually decline with increasing age, and for many women, testosterone levels start to decline from their late 20s [1].
This decline in testosterone is often associated with adverse symptoms including low mood, anxiety, reduced stamina, poor sleep, headaches, worsening migraines, muscle and joint pains and urinary symptoms [2].
Many women have testosterone levels undertaken by having a blood test.
How can a testosterone level of <0.08 nmol/L (<2.31 ng/dL) be ‘normal’?
Testosterone levels from blood results often cause confusion for both women and clinicians. I have consulted with many women at my Newson Clinic who have been wrongly told that their testosterone level from their blood test is ‘normal’, yet their levels may have been undetectable. These women have symptoms of testosterone deficiency but have wrongly been told they would not benefit from being prescribed testosterone.
The ‘normal’ range for a particular blood test can often be standardised: for example, when testing for the diabetes marker HbA1c, there is an internationally agreed reference range, regardless of which laboratories your local GP or hospital uses.
However, this is not the case for all tests, and where there are no internationally or nationally agreed reference ranges, laboratories either have to develop their own, source a reference from published work, or, more often than not, for testosterone, they use the test manufacturer's recommended range. Which, although easier, is not always ideal, as you will read about in this article.
Why is there so much confusion and uncertainty in interpreting testosterone blood test results?
Firstly, there are no standardised reference ranges for serum testosterone concentrations in women [3]. This is because comprehensive studies have not been published, and there is constant debate with clinicians regarding testosterone testing and reference ranges. This is despite studies showing over the past 80 years the many benefits of testosterone in women!
So, how can we interpret testosterone blood test results?
Firstly, it is important to know that testosterone blood tests are simply a guide. Testosterone is produced by various organs, including your ovaries, adrenal glands and your brain [3], and levels of testosterone can vary naturally throughout the day. At certain times of the day, testosterone levels are higher than others, and there can be variation of levels throughout the day, even when you are using testosterone cream or gel.
Frustratingly, as discussed above, there is no nationally agreed upon testosterone ‘normal' level for women. This means that the laboratories will report different levels as 'normal', depending on where they obtained their reference range data.
In addition, some laboratories have different reference ranges for women at different ages which does not make any sense. In the case of testosterone, this is lower in older women than in younger women. Yet women are all different and their testosterone declines at different ages.
However, avoiding testosterone can result in negative consequences for women. If women of any age with low testosterone are prescribed testosterone, then both their symptoms and their future health usually improve [4, 5].
In the UK, there are four main manufacturers of hormone blood tests. In the instructions for use for these tests, the manufacturer will provide a ‘normal’ reference range. However, this data is often derived from very small sample sizes.
There are internationally agreed-upon processes for calculating reference ranges (CLSI EP28-A3c). This guideline recommends a minimum of 120 healthy reference individuals per partition (e.g., for each sex or age group). Where there are sex, ethnicity, or age-related differences, such a small number is unlikely to yield sufficient data to be representative of the whole population; therefore, the accuracy of that data is heavily dependent on the group used by the manufacturer.
As an example, one manufacturer's female testosterone reference range is based on just 160 women who were ‘apparently healthy’. Out of the 160 women, only 71 were over 50. Unfortunately, it is not known if any of these women were experiencing symptoms of low testosterone, thereby skewing the data. This situation, however, is common, and the other manufacturers of testosterone blood tests also use their own reference ranges, again based on a very low number of women.
Therefore, some laboratories will resort to peer-reviewed published data. But even using this type of data can often be of little help. In one review paper, several studies, some including female athletes, reported that it is normal for women to have a testosterone level of 0 – which is nonsensical [6].
It's well known that testosterone is critical for maintaining good health. For example, there is now substantial evidence that testosterone levels are positively associated with bone mineral density in both men and women [7].
Here are a few examples of some NHS laboratories stating their current testosterone normal reference ranges for women:
* Gloucester NHS Trust uses <1.8 nmol/L. This is used by several other NHS Trusts, including Leeds and Cambridge [8]
* University of North Midlands uses 0.0 – 1.3 nmol/l for women over 50 years of age [9]
* Liverpool Foundation Trust uses <1.9 nmol/l [10].
Here are a few examples of some US laboratories stating their current testosterone normal reference ranges for women:
* Labcorp: Premenopausal range 10-55 ng/dL and Postmenopausal 7-40 ng/dL) [11]
* Quest: Women ≥18 years: 2–45 ng/dL [12]
* Mayo Clinic Labs: 17-18 years: 20-75 ng/dL or >19 years: 8-60 ng/dL [13]
What should you do if you are told that your testosterone level is normal?
You should ask for the actual number rather than just be told it is normal, especially if you have symptoms that could be related to low testosterone in your body.
If your level is low and you would like a trial of testosterone treatment, then you should make a consultation with a doctor who understands testosterone and is experienced in testosterone prescribing. If you are in the UK, the experienced clinicians at Newson Clinic can help you.
If you are taking testosterone, then you should also find out your actual level. Some women are told their level is too high and are encouraged to reduce their dose or stop taking their testosterone. A single testosterone result is only a snapshot; therefore, this one-off level may not reflect your true physiological level, and a repeat is usually required.
What should women do if their testosterone levels are raised?
In medicine, any blood test result needs to be interpreted in a clinical context by a clinician who understands both hormones and patients. I know this sounds obvious, but I have seen so many patients in my clinic who have raised testosterone levels, have no side effects and have felt really well.
So rather than worrying and telling them to reduce or stop their testosterone, I ask them to repeat the blood test, and then the testosterone blood test usually comes back as normal.
Side effects from testosterone are very uncommon and are usually reversible. The most common side effect is some hair growth at the site of cream application (which is not dose-dependent). Systemic side effects such as facial hair, voice changes and enlarged clitoris are very uncommon when prescribed at the right dose.
