The key hormones in female health

Oestrogen

Oestrogen is the hormone most associated with female biology. It does more than most people realise.

What it does

Oestrogen drives most of what makes a female body female. Breast development, body shape, the menstrual cycle, the uterine lining, bone density, brain function, skin elasticity, cholesterol patterns, fat storage and many more processes all involve oestrogen. The hormone is not just about reproduction. It influences almost every system in the body.

Where it comes from

Mostly the ovaries during reproductive years. Smaller amounts come from fat tissue, the adrenal glands and other sources. After menopause the ovaries stop producing oestrogen and fat tissue becomes the main source of the small amounts that remain. This is why body composition affects post menopausal oestrogen levels.

How it changes

Oestrogen rises through puberty, fluctuates through each menstrual cycle, peaks at ovulation, drops in the late luteal phase and remains low after menopause. Pregnancy produces massive oestrogen levels. Perimenopause produces wild fluctuations. The variation is huge across the lifespan.

Why levels matter

Too much or too little oestrogen at the wrong time produces problems. Excess oestrogen relative to progesterone contributes to heavy periods, fibroids and some cancers. Too little oestrogen produces menopausal symptoms, bone loss and other issues. The balance with other hormones often matters more than absolute levels.

Progesterone

Progesterone gets less attention than oestrogen but is equally important. It balances oestrogen and has its own range of effects.

What it does

Progesterone is produced after ovulation and prepares the uterine lining for a potential pregnancy. It also has effects on mood, sleep, body temperature, breast tissue and several other systems. Many of the symptoms of the second half of the menstrual cycle relate to progesterone. The calming effect of progesterone for some women contrasts with the more energetic effect of oestrogen.

When it is produced

Only after ovulation. In cycles where ovulation does not happen, progesterone is not produced. This matters because the absence of ovulation often leads to oestrogen dominance, which contributes to heavy periods and other symptoms. Progesterone production peaks about a week after ovulation and falls in the days before a period.

The pregnancy role

Progesterone is essential for maintaining pregnancy. Levels rise dramatically through the first trimester then plateau at high levels for the rest of pregnancy. The drop in progesterone after birth (along with oestrogen) contributes to the baby blues and is part of why postpartum hormonal changes feel so intense.

When it falls early

Progesterone production typically declines earlier in perimenopause than oestrogen because it depends on ovulation, which becomes less reliable. This is part of why cycles often become heavier and PMS more troublesome during perimenopause. The relative excess of oestrogen produces the perimenopausal pattern.

FSH LH and the brain hormones

The brain controls the ovaries through specific hormones. Knowing these helps make sense of how the whole system runs.

FSH and LH

The pituitary gland produces FSH (follicle stimulating hormone) and LH (luteinising hormone). FSH tells the ovaries to mature eggs. LH triggers ovulation. Both rise and fall in characteristic patterns through the cycle. Blood tests can measure both, though levels fluctuate too much in perimenopause to be diagnostically useful in most cases.

The feedback loop

The brain monitors oestrogen and progesterone and adjusts FSH and LH accordingly. The whole system runs as a feedback loop. As ovaries become less responsive in perimenopause, the brain compensates by increasing FSH. This is why post menopausal FSH levels are very high.

GnRH

The hypothalamus produces gonadotropin releasing hormone (GnRH) which controls the pituitary. GnRH is the master switch of the whole reproductive hormonal system. Stress, illness, poor sleep, inadequate energy intake and other factors can suppress GnRH and disrupt the entire downstream cascade. This is the mechanism by which life events affect cycles.

Prolactin

Made by the pituitary, prolactin drives milk production and suppresses ovulation during breastfeeding. High prolactin in non breastfeeding women can disrupt cycles and cause other symptoms. Speak to your GP if you have irregular cycles, milk discharge from breasts when not breastfeeding or unexplained fertility difficulties.

Testosterone and beyond

Several other hormones play important roles in female health. They are often overlooked in discussions of female hormones but matter.

Testosterone

Women produce smaller amounts of testosterone than men but it still matters. Testosterone supports libido, energy, muscle and mood. Levels decline through the thirties and forties and drop more sharply around menopause. Low testosterone can contribute to symptoms that persist after starting oestrogen HRT. Testosterone HRT is available in the UK but less commonly prescribed than oestrogen.

Cortisol

The stress hormone interacts with all the others. Chronic high cortisol disrupts the reproductive hormonal cascade through effects on GnRH. This is the mechanism by which prolonged stress affects cycles and fertility. Cortisol also affects insulin sensitivity, sleep and many other systems relevant to female health.

Thyroid hormones

The thyroid produces hormones that regulate metabolism throughout the body. Both under and overactive thyroid affect cycles, mood, energy and fertility. Thyroid issues are particularly common in women. Blood tests for thyroid function should be part of any workup for unexplained female symptoms. Postpartum thyroiditis affects 5 to 10 percent of women.

Insulin

Insulin is not usually thought of as a reproductive hormone but its effects on female health are significant. Insulin resistance contributes to PCOS, affects ovulation and influences body composition. Improving insulin sensitivity often improves PCOS symptoms substantially. The hormonal systems all interact.

More on female health

For oestrogen in depth our Oestrogen: What It Does and Why It Matters covers the main female hormone. Progesterone: What It Does and Why It Matters covers the other half. And The Four Hormonal Phases of the Menstrual Cycle covers how they all interact.