Hormonal health in men over 40
Testosterone production peaks in men during late adolescence and their thirties, then begins to decline gradually at a rate of between 1 per cent and 2 per cent per year from the age of 30 to 40. Unlike the menopause in women, which occurs at a specific and clearly defined stage, the decline in male sex hormones is a gradual and silent process, making it a real challenge to recognise the symptoms.
This article examines the causes of hormonal decline in men over the age of 40, its most prominent symptoms, and the natural supplements whose effectiveness in supporting this system has been proven by randomised clinical trials — whilst clearly distinguishing between what is supported by evidence and what is not.
The mechanism of hormonal decline in men — what happens biologically?
Testosterone is primarily produced in Leydig cells in the testicles, in response to the hormone LH released by the pituitary gland, which in turn responds to the hormone GnRH released by the hypothalamus. This axis is known as the HPG (Hypothalamic-Pituitary-Gonadal Axis). With advancing age, the function of the HPG axis declines across three simultaneous levels: a reduction in the hypothalamus’s sensitivity to feedback signals, a decline in the pituitary gland’s response to LH secretion, and a decrease in the efficiency of Leydig cells in converting cholesterol into testosterone. A clinical review has documented an in-depth analysis of these mechanisms, noting that modifying factors such as chronic stress, obesity and sleep deprivation significantly accelerate this decline.
Added to this is the age-related rise in protein levels, which binds to and restricts free testosterone, thereby reducing the amount actually available to cells — even if total testosterone levels appear normal in blood tests.
Common symptoms of declining testosterone levels after the age of 40
The symptoms fall into several categories:
- Energy and physical performance: unexplained chronic fatigue, a decline in muscle strength, difficulty building muscle mass despite regular exercise, and an increase in visceral fat, particularly around the abdomen.
- Mental health and mood: mood swings, difficulty concentrating and mild brain fog, reduced motivation and self-confidence, and sleep disturbances.
- Sexual health: reduced sexual desire, and changes in sexual performance linked to a decrease in free testosterone.
- Bone health: Testosterone helps maintain bone density, and a decline in its levels increases the long-term risk of osteoporosis.
The most widely studied natural supplements for supporting hormonal balance in men
1. Ashwagandha — the most potent of the herbs
Ashwagandha is one of the plant compounds for which the most reliable clinical evidence has been gathered in the context of men’s hormonal health. A comprehensive clinical review concluded that ashwagandha has the strongest evidence of any herb studied for raising testosterone levels. Another study conducted on healthy adult men demonstrated improvements in indicators of sexual health and testosterone levels after 8 weeks of taking a standardised ashwagandha root extract. This effect is attributed to two complementary mechanisms: a reduction in chronic cortisol, which inhibits the HPG axis, and a potential direct effect on Leydig cells.
2. Zinc — the mineral most closely associated with testosterone production
Zinc plays a pivotal role in activating the enzymes responsible for converting cholesterol into testosterone within Leydig cells, and it also inhibits the enzyme aromatase, which converts testosterone into oestrogen. A review in ScienceDirect concluded that zinc, vitamin D and ashwagandha are the supplements most strongly supported by randomised controlled clinical trials in raising testosterone levels in men with low testosterone.
Zinc deficiency is common in Saudi Arabia due to the prevalence of diets low in animal protein and high in grains containing phytates, which inhibit zinc absorption.
3. Vitamin D — more a hormone than a vitamin
Vitamin D has receptors on Leydig cells in the testicles, meaning that its link to testosterone production is a direct biological one, rather than merely a statistical correlation. A 2023 review concluded that there is a positive correlation between vitamin D levels and testosterone, noting that the effect is most pronounced in those with vitamin D deficiency, whilst it is less pronounced in those whose levels are already sufficient.
4. Magnesium — Supporting free testosterone and reducing SHBG
Magnesium binds to SHBG, thereby reducing this protein’s binding to testosterone and consequently increasing the proportion of free testosterone available to cells. Magnesium is also involved in over 300 enzymatic reactions, including those associated with the synthesis of sex hormones. A review has indicated that magnesium supports the biological activity of testosterone by reducing its binding to SHBG, with the added benefit of improving sleep quality, which in turn is an independent factor in supporting hormone production.
Lifestyle factors — the foundation before supplements
The PMC integrative review (2025) showed that improving lifestyle factors often produces a faster and more pronounced effect on testosterone levels than supplements alone:
- Adequate sleep: Around 70 per cent of daily testosterone is produced during deep sleep phases — sleeping for less than 5 hours reduces levels by as much as 10–15 per cent.
- Resistance training: Strength training has been documented to stimulate testosterone production via the HPG axis.
- Reducing cortisol: Chronic stress competes with testosterone for pregnenolone, the common precursor to both.
- Healthy weight: Adipose tissue converts testosterone into oestrogen via the enzyme aromatase — the more visceral fat there is, the higher the rate of this conversion.
Marnys® products to support men’s health
Exotique Plus contains plant extracts designed to support vitality and physical performance, whilst the zinc and selenium product provides a comprehensive mineral formula that supports the function of enzymes involved in testosterone production. Marnys® Vitamin D3 and Magnesium products also support the second and third levels of hormonal balance in men over 40.
Frequently Asked Questions
Is a decline in testosterone after the age of 40 inevitable? A gradual decline of 1–2 per cent per year is normal and to be expected, but modifying factors such as chronic stress, obesity and lack of sleep accelerate it significantly — and addressing these makes a greater difference than supplements alone.
Is it possible to boost testosterone naturally without hormone therapy? Yes, in cases of natural age-related decline, nutrient deficiencies or stress — but clinically confirmed testosterone deficiency, as evidenced by laboratory tests, may require specialist medical intervention.
Is ashwagandha safe for long-term use? The safety profile is acceptable in available studies lasting up to 24 weeks, but long-term data are limited and require regular medical monitoring.
When should a testosterone test be carried out? It is advisable to have it done in the morning between 8 and 10 am, as testosterone levels peak at this time. It is preferable to have two tests carried out on separate days before making any treatment decisions.
Summary
Hormonal decline after the age of 40 is a natural physiological phenomenon; however, its rate and severity are not inevitable. The available clinical evidence provides clear support for specific supplements — notably ashwagandha, zinc, vitamin D and magnesium — but within a specific context: their effectiveness is enhanced when nutritional deficiencies are corrected and lifestyle factors affecting hormone production are addressed, and they are no substitute for a medical assessment where clinically documented hormonal insufficiency is suspected.
