Hormones & HRT - The basics
Hormones 101: the ones that matter and why
A plain-English introduction to the major hormones - what they are, the systems they coordinate, and why small shifts can be felt across the whole body.
Hormones are chemical messengers. Glands release them into the bloodstream, and they travel to distant tissues where they switch processes on or off. Because a single hormone can act on many organs at once, the body uses them to coordinate things that need to happen together - growth, metabolism, the stress response, reproduction and sleep. That reach is also why a modest change in one hormone can be noticed in several unrelated-seeming ways.
The ones most people ask about
A handful of hormones come up again and again in conversations about ageing and wellbeing. Understanding roughly what each does makes the rest of this classroom easier to follow.
- Oestrogen and progesterone - central to the menstrual cycle and reproductive health, with wider roles in bone, mood and the lining of blood vessels.
- Testosterone - present in everyone, higher on average in men, involved in muscle, bone, libido and mood.
- Thyroid hormones - set the pace of metabolism across nearly every cell.
- Cortisol - the main stress hormone, following a daily rhythm and shaping energy and blood sugar.
- Insulin - governs how the body stores and uses glucose.
Feedback loops keep things in range
The body rarely lets a hormone drift unchecked. Most sit inside feedback loops: the brain senses the level in the blood and dials production up or down, much like a thermostat. This is why a single measurement in isolation can be misleading, and why interpreting hormones is a job for a clinician who can read the whole picture - symptoms, history and the loop, not one number.
Nothing here tells you whether your own hormones are high, low or normal. That is a clinical judgement. The aim of this lesson is only to give you the vocabulary to have a more informed conversation.
This classroom is educational and is not medical advice. It cannot tell you anything about your own hormone levels or what to do about them. Any decision involving hormones must be made with a qualified doctor who knows your history - treat this as background to inform that conversation, not a substitute for one.
Sources for this classroom
Educational content only. Not medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before changing your health regimen.
