Most people notice the effects of ageing before they understand what is causing them. Energy that used to be reliable starts to dip. Recovery takes longer. Body composition shifts despite no obvious change in diet or exercise. Sleep becomes lighter. Motivation fluctuates.
These are not imagined. They may be the downstream effects of biological changes that begin earlier than most people expect. The rate and impact of these changes varies significantly between individuals.
The hormonal shift starts in your 30s
Growth hormone output declines steadily from your mid-20s. By your 40s, many people are producing a fraction of what they produced at peak. Growth hormone is not just about height. In adults, it plays a central role in:
- Body composition (lean muscle versus fat mass)
- Sleep quality, particularly deep slow-wave sleep
- Cellular repair and recovery
- Mood and cognitive function
Testosterone also begins declining in men from around the early 30s. The decline is gradual, roughly 1-2% per year on average, but it compounds. By the time many men notice symptoms, the cumulative change is significant. Women experience more dramatic hormonal shifts through perimenopause, which can begin a decade before menopause.
Thyroid function can become less efficient with age, as can the sensitivity of cells to thyroid hormone. DHEA, produced by the adrenal glands, is the precursor to many sex hormones and immune-modulating compounds. It peaks in your mid-20s and declines progressively.
Metabolic changes
Insulin sensitivity tends to decline with age, even in people who maintain a healthy weight. Cells become less responsive to insulin signals, which affects how efficiently you convert food to energy versus how much gets stored as fat.
Inflammation markers tend to rise with age in what researchers sometimes call “inflammageing”. This low-grade, chronic inflammatory state is associated with changes in immune function, joint health, cognitive performance, and metabolic efficiency.
Cellular and repair biology
Every cell in your body divides a finite number of times. Telomeres, the protective caps at the end of chromosomes, shorten with each division. Shorter telomeres are associated with accelerated cellular ageing. The rate of telomere shortening is influenced by lifestyle factors including sleep quality, stress levels, exercise, and nutrition.
Mitochondrial function, the cellular machinery that produces energy, also tends to decline with age. This is one of the drivers of the fatigue and reduced exercise capacity many people notice in their 40s and beyond.
Why individual biology matters
The rate at which these changes occur varies enormously between individuals. Genetics plays a role, but so do lifestyle, environment, and the degree to which hormonal and metabolic shifts are identified and addressed early.
Two people the same age can have very different biological profiles. One may have growth hormone levels comparable to someone a decade younger. Another may show significant hormonal decline that is not yet causing obvious symptoms but will in the near future.
This is why biological age markers, assessed through comprehensive blood work and health history, are more informative than chronological age.
The assessment-first approach
Supporting healthy ageing starts with understanding your individual biology. A comprehensive assessment can help establish your baseline across relevant markers, hormonal, metabolic, and immune, and identify which areas, if any, may warrant further discussion with your practitioner.
From that point, a practitioner may, if clinically appropriate, design a protocol around what the assessment finds. Individual results vary and outcomes cannot be guaranteed.
Curious about your biological age markers? Start your free assessment. A practitioner reviews your answers and your goals.
Disclaimer: Individual results vary. All protocols are subject to practitioner assessment and clinical suitability. Nothing in this article constitutes medical advice.
