Why Hormones Are Declining in Men & Women — The Science Behind the Silent Crisis

Something is happening to human hormones on a civilisational scale. Testosterone has been falling for decades. Fertility rates are at historic lows. Millions of women battle progesterone deficiency without a diagnosis. This isn’t just ageing — it’s a crisis with identifiable culprits. Harvard Health on dietary supplements — sorting out the science is worth reading before anyone sells you a hormone “fix” in a capsule.

If you’ve ever felt persistently fatigued, noticed your body composition shifting despite no dietary changes, experienced low libido, disrupted sleep, brain fog, or a persistently flat mood — your hormones may be telling you something your blood tests aren’t catching yet.

The endocrine system — the network of glands that produce and regulate hormones — is arguably the most sensitive system in the human body. Tiny concentrations of hormones govern everything from your energy and mood to your muscle mass, bone density, and immune response. Which is precisely why the modern environment poses such a profound threat to it.

The hormones under threat

While the endocrine system produces over 50 identified hormones, a handful sit at the centre of this modern crisis. Understanding what they do — and what it feels like when they fall — is the first step.

The seven major causes of decline

The data is unambiguous: hormone levels are falling across generations independent of age. A 35-year-old man today has measurably lower testosterone than a 35-year-old in 1985. This is not a genetic shift — it is environmental and lifestyle-driven.

• 01
  Endocrine disrupting chemicals (EDCs)

  Xenoestrogens found in plastics (BPA), food packaging, cosmetics, pesticides, and receipts mimic oestrogen and interfere with natural signalling. Phthalates suppress testosterone in Leydig cells. These are measurable in blood and urine across the general population — not theoretical risks.

• 02
  Chronic stress & cortisol dominance

  Cortisol and sex hormones share a precursor: pregnenolone. Under sustained stress, cortisol is prioritised at the expense of testosterone and progesterone — a phenomenon called “pregnenolone steal.” Modern working life creates chronic cortisol elevation that quietly depletes the hormonal system.

• 03
  Sleep deprivation & circadian disruption

  The majority of testosterone is synthesised during deep sleep. Restricting sleep to five hours for just one week reduces testosterone by 10–15% — equivalent to ageing a decade. Blue light, irregular schedules, and poor sleep architecture disrupt pulsatile hormone release from the pituitary.

• 04
  Ultra-processed foods & nutritional deficiency

  Hormones are built from fats and cholesterol. Low-fat diets and seed-oil-dominant ultra-processed foods create deficiencies in zinc, vitamin D, and magnesium — all essential for hormone synthesis. Most of the UK population is deficient in at least two of these.

• 05
  Excess body fat & aromatisation

  Fat tissue contains aromatase, which converts testosterone into oestrogen. As body fat rises, aromatase activity increases — creating a feedback loop that further suppresses testosterone and drives oestrogen dominance in both men and women.

• 06
  Sedentary living & overtraining

  Both extremes suppress hormones. Sedentariness reduces insulin sensitivity and anabolic signalling. Excessive endurance training without recovery raises cortisol and can induce functional hypogonadism. Consistent resistance training with adequate rest is the hormonal sweet spot.

• 07
  Microplastics & environmental contamination

  Emerging research identifies microplastics as a new hormonal threat. Found in blood, lung tissue, breast milk, and testes, microplastics carry phthalates and bisphenols. A 2023 study found them in every human testis analysed, with concentrations correlating inversely with sperm quality.

Symptoms often missed as hormonal

Because hormonal decline is gradual, it is rarely the first diagnosis explored. The symptoms below are frequently hormonal in origin — in both men and women — and are routinely attributed to stress or ageing.

A cluster of these symptoms, alongside the lifestyle exposures described above, warrants a comprehensive hormone panel — total and free testosterone, oestradiol, SHBG, LH, FSH, progesterone, DHEA-S, cortisol, and thyroid markers — which gives a far more complete picture than standard GP testing.