What's actually happening to your hormones in your 40s
Most men in their 40s notice something has shifted. The energy is not quite there. Recovery from exercise takes longer. Sleep feels less restorative. The weight sits stubbornly around the middle. The usual explanations are stress, age, work. But there is also a physiological explanation that gets far less attention: your testosterone is declining.
What happens to your hormones in your 40s
Testosterone begins declining gradually from around age 30, at approximately one to two percent per year. By your mid-40s, levels are meaningfully lower than they were in your 20s — not dramatically in most cases, but enough to have cumulative effects on energy, body composition, mood, libido and cognitive function.
This process is sometimes called andropause, or more accurately late-onset hypogonadism. Unlike female menopause, it is not a distinct biological event but a gradual shift. The absence of a dramatic threshold is part of why it goes unrecognised — symptoms accumulate slowly enough that many men attribute them to other causes.
SHBG (sex hormone binding globulin) also tends to increase with age, binding to testosterone in the bloodstream and reducing the amount of free testosterone available to your tissues. A blood test measuring total testosterone can appear within the normal range while free testosterone is significantly lower. Standard GP testing frequently misses this.
Cortisol is also relevant. Sustained high cortisol — driven by work pressure, poor sleep, chronic stress, excess alcohol — directly suppresses testosterone production. A high-stress lifestyle in your 40s accelerates testosterone decline.
The symptoms worth taking seriously
Persistent fatigue
Not the tiredness that resolves after a good night's sleep. A sustained reduction in energy and drive that does not lift regardless of rest. Testosterone plays a central role in energy metabolism, and its decline combined with poorer sleep quality creates a feedback loop that compounds over time.
Changed body composition
Fat accumulating around the abdomen despite no significant change in diet or exercise. Muscle that is harder to build and easier to lose. Testosterone is anabolic — it supports muscle protein synthesis. As levels fall, the balance tips toward fat storage, particularly visceral fat. This type of fat is metabolically active and increases cardiovascular risk.
Reduced libido
Testosterone is the primary driver of sexual desire in men. Its decline is the most common hormonal cause of reduced libido. This is direct and physiological. It is not a relationship problem and not something you simply have to accept.
Mood and motivation
Testosterone influences dopamine pathways and overall drive. Low testosterone is associated with reduced motivation, increased irritability, low mood, and in some men a flat or joyless quality to daily life that does not fit the profile of clinical depression but sits somewhere in that territory.
Sleep changes
Testosterone is produced primarily during deep sleep. Poor sleep suppresses testosterone. Lower testosterone worsens sleep quality. Once this cycle is established it compounds. Many men in their 40s notice they are sleeping more lightly and not feeling restored by sleep.
What blood tests are worth considering
The Men's Hormone Panel measures total testosterone, free testosterone, SHBG, LH, FSH and prolactin. Free testosterone is the critical number that standard testing misses. A blood test that comes back "normal" on total testosterone can still show significantly low free testosterone — the amount your body can actually use.
A Full Thyroid Panel is also worth including. Thyroid dysfunction produces symptoms almost identical to low testosterone, and both conditions can be present simultaneously.
What actually helps
If your testosterone is clinically low — TRT
Testosterone replacement therapy is a legitimate medical treatment for men with clinically low testosterone. Prescribed, monitored TRT uses doses designed to restore testosterone to the normal physiological range. Evidence supports TRT for improving energy, libido, body composition, mood and bone density in men with diagnosed hypogonadism.
Strength training
The most evidence-based non-medical intervention for testosterone support. Compound movements performed with adequate load three times per week have been shown to support better long-term testosterone levels. More effective than cardio alone.
Sleep
Testosterone is produced during deep sleep. Anything that improves sleep quality — consistent sleep and wake times, a cool dark room, alcohol reduction, limiting screen time before bed — directly supports testosterone production.
Reducing alcohol
Alcohol suppresses testosterone production directly and disrupts the sleep during which testosterone is synthesised. Even moderate regular intake has a measurable effect. Reducing intake to low levels has measurable benefits.
Supplements worth considering
Zinc is essential for testosterone synthesis. Deficiency directly impairs production. Vitamin D3 — deficiency is associated with lower testosterone levels. Ashwagandha (KSM-66) has the strongest evidence base among herbal supplements for testosterone support, with studies showing reductions in cortisol and improvements in strength and recovery. Magnesium glycinate is a cofactor in testosterone production and commonly depleted in men who exercise regularly or consume significant alcohol.
When to see a specialist
- If you are experiencing significant symptoms and want your testosterone tested
- If a home test returns low or borderline-low results
- If you are experiencing erectile dysfunction — this warrants cardiovascular assessment
- If you want a referral to an endocrinologist or urologist for a specialist assessment