Perimenopause is the transitional period leading to menopause, characterised by increasingly erratic oestrogen and progesterone production as the ovaries begin to wind down. It typically starts in the mid-forties, occasionally earlier, and ends at menopause, defined as 12 consecutive months without a menstrual period. The average age of menopause in the UK is 51. This means the average woman spends four to eight years in perimenopause, often without knowing that is what is happening.
Why the Symptoms Are Frequently Missed
Perimenopausal hormone fluctuation does not produce a steady, predictable decline. Oestrogen levels can swing dramatically, rising above normal and then falling, creating a pattern of symptoms that are highly variable day to day and month to month. Irregular periods, poor sleep, increased anxiety, brain fog, joint pain, changes in body composition, and reduced recovery from exercise are all recognised symptoms of perimenopause. They are also commonly attributed to stress, depression, overwork, or simply ageing. The connection to hormonal transition is frequently missed, sometimes for years.
The Key Hormonal Shifts
Progesterone declines first, often producing poor sleep quality, increased anxiety, and irregular cycles. Oestrogen becomes erratic, sometimes elevated, sometimes low, creating the characteristic symptom fluctuation. FSH rises as the pituitary attempts to stimulate failing ovaries, and this is the hormone most commonly measured to confirm the menopausal transition. Testosterone also declines through this period, contributing to reduced energy, muscle loss, and diminished drive.
Clinical Options Worth Discussing
- HRT started in perimenopause has the strongest evidence base for long-term benefit; earlier initiation is associated with better cardiovascular and cognitive outcomes
- Micronised progesterone appears safer than synthetic progestins and specifically improves sleep quality
- Transdermal oestrogen has a lower clot risk than oral oestrogen
- Testosterone replacement for women is supported by evidence for libido, energy, and cognitive function, though it is less routinely prescribed
- Non-hormonal options including SSRIs, CBT, and structured exercise show meaningful benefit for specific symptoms including vasomotor symptoms and mood
- Resistance training is among the most effective single interventions for perimenopausal body composition changes
Sources
- Santoro, N., et al. (2016). Menopausal symptoms and their management. Endocrinology and Metabolism Clinics of North America, 44(3), 497-515.
- NICE Guideline NG23. (2023). Menopause: diagnosis and management. National Institute for Health and Care Excellence.
- Soules, M.R., et al. (2001). Stages of Reproductive Aging Workshop (STRAW). Fertility and Sterility, 76(5), 874-878.