Testosterone and other hormone tests, and how to read them well

What the tests are

A hormone profile measures the messengers that control energy, mood, sexual function and fertility. In men the central test is total testosterone, often with sex hormone binding globulin (SHBG), which lets the laboratory estimate the free, active portion, and luteinising hormone (LH), which shows whether the testes or the pituitary gland is the source of a low level [1].

Thyroid testing usually starts with thyroid stimulating hormone (TSH). NICE suggests adding free thyroxine (FT4) when TSH is high, and FT4 with free tri-iodothyronine (FT3) when it is low [2].

Why it is done and who it is for

For men, testing makes sense when there are symptoms. In a European study of 3,369 men aged 40 to 79, the sexual symptoms, including poor morning erections and low desire, were the ones most closely linked to low testosterone [3]. Guidelines advise diagnosing testosterone deficiency only when such symptoms come with consistently low results [4].

Thyroid tests suit anyone with symptoms that suggest an under or overactive thyroid, and NICE notes that in women around menopause, thyroid symptoms can be mistaken for menopause [2].

Who it is not for

If you are 45 or over with hot flushes and changing periods, NICE advises recognising perimenopause from your symptoms, without blood tests [5]. Tests such as oestradiol and anti-Müllerian hormone should not be used to identify perimenopause or menopause at that age [5].

A testosterone test during an acute illness, or a thyroid test while you are acutely unwell, may give a misleading result, so it is better to wait until you have recovered [1] [2]. If you have chest pain, severe breathlessness, a racing heart with fainting or sudden confusion, call 999 in the UK or the local emergency number elsewhere.

Benefits and limitations

The benefit is a clear answer to a specific question, such as whether tiredness has a thyroid cause or whether low desire has a hormonal one. A normal result is useful too, because it moves the conversation to sleep, stress, weight and other causes.

The limitation is that one result rarely settles it. Testosterone varies through the day, and subclinical thyroid changes are confirmed on 2 separate tests 3 months apart before treatment is considered [2].

Risks

The blood draw is low risk, with a small chance of a bruise or feeling faint. The real risk is a wrong conclusion. A single low afternoon result can start treatment that was never needed, and testosterone treatment reduces sperm production, so it is not started in men planning a family soon [4] [1].

How you prepare

For testosterone, come between 7am and 11am, ideally fasting for the first test [1]. In men aged 30 to 40, levels were 20 to 25% lower in the afternoon than at 8am [6]. A low result is repeated on at least 2 occasions, preferably 4 weeks apart [1].

Tell the doctor about any biotin supplement, because high doses can make thyroid results falsely high or low [2]. Women using combined hormonal contraception should know that FSH cannot identify menopause while they take it [5].

• A list of your medicines and supplements, including biotin
• Previous hormone or thyroid results, with the time of day they were taken
• Your main symptoms and when they began
• For women, the dates of your recent periods and any contraception

Results and common errors in reading them

In men with symptoms, the British Society for Sexual Medicine treats total testosterone below 12 nmol/L, or free testosterone below 225 pmol/L, on two separate morning samples, as usually needing treatment [1]. Between 8 and 12 nmol/L it advises measuring free testosterone, and below 12 it adds LH and FSH to find the cause [1].

• Testing in the afternoon, when testosterone is naturally lower
• Acting on one result instead of a confirmed pair
• Reading a laboratory reference range as a treatment threshold [1]
• Missing the effect of biotin on thyroid results
• Using FSH to diagnose menopause in women over 45 [5]
• Retesting thyroid sooner than 6 weeks after the last test [2]

Questions to ask your doctor

These help you leave with an answer rather than a number.

• Was my sample taken at the right time of day?
• Do I need a second test before we decide anything?
• What else could explain my symptoms?
• If I start treatment, how will we know it is working and safe?

How The Wellness can help

Advanced Health includes a hormone profile and full thyroid tests, with PSA for men and a priority call from a GP. Longevity+ adds advanced hormones within a wider profile and a written plan. If you would rather start with a conversation, a GP appointment lets you decide which tests are worth doing.

Our clinics on Baker Street in Marylebone and Eccleston Street in Belgravia open early every day. Every doctor is GMC registered, and samples go to accredited laboratories.