Understanding hormones, and hormone replacement therapy (HRT)

Need a hormone 101 to understand what’s going on, and where to start with HRT?

We’ve got you. Here’s a deep (but not too science-y) look at the role oestrogen, progesterone and testosterone play in our bodies, and how HRT helps.

Why hormones matter after surgery

Your ovaries are far more than reproductive organs — they’re powerful hormone producers that support almost every system in your body. When they’re removed, levels of oestrogen, progesterone and testosterone drop suddenly and completely, triggering surgical menopause.

This hormonal loss affects your brain, heart, bones, skin, joints, muscles, and mood, and can leave you feeling like your body and mind have changed overnight. Hormone Replacement Therapy (HRT) helps to restore balance by replacing what your ovaries would have produced naturally, protecting both your short- and long-term health.

Research consistently shows that starting HRT soon after ovary removal reduces the risk of heart disease, osteoporosis, dementia, depression, and all-cause mortality (Faubion et al., Climacteric 2015; Kaunitz et al., JAMA 2021).

Key Facts

  • The ovaries produce oestrogen, progesterone, and testosterone — hormones essential for bone, heart, brain, and emotional health.

  • After surgical menopause, these hormones fall abruptly; HRT replaces what your body would have produced naturally until around age 51.

  • Body-identical hormones (17β-estradiol, micronised progesterone, and testosterone cream) are the safest and most effective forms of replacement.

  • Transdermal oestrogen is preferred for most women, with lower clot and stroke risk than tablets.

  • Only 4.8% of eligible UK women currently receive HRT after ovary removal (Cashell et al., Menopause 2024).

Oestrogen

What oestrogen does in the body

Oestrogen is the dominant female sex hormone, and it influences almost every tissue. Beyond regulating your menstrual cycle, it:

  • Protects heart health by maintaining healthy blood vessel walls and regulating cholesterol.

  • Keeps bones strong by slowing calcium loss and preventing bone breakdown.

  • Supports brain function, particularly memory, focus, and mood regulation.

  • Maintains skin elasticity and collagen production, keeping tissue supple.

  • Nourishes the vaginal and urinary tract, maintaining moisture and reducing infection risk.

  • Modulates body temperature, helping to prevent hot flushes and night sweats.

When the ovaries are removed, oestrogen levels crash within days, leading to symptoms such as:

  • Hot flushes and night sweats

  • Anxiety, low mood and irritability

  • Brain fog and poor concentration

  • Vaginal dryness and urinary issues

  • Joint pain, fatigue, and disturbed sleep

Over time, the long term impact of low oestrogen also increases the risk of osteoporosis, heart disease, and cognitive decline.

Replacing oestrogen

Oestrogen can be replaced in several ways, depending on personal preference, absorption, and medical history.

1. Transdermal oestrogen (patch, gel, or spray)
Delivers oestrogen through the skin directly into the bloodstream. This is the preferred route after surgical menopause because it:

  • Avoids the liver, reducing the risk of blood clots, stroke, or raised triglycerides.

  • Provides steady hormone levels with fewer side effects.

  • Is suitable for women with migraines, higher BMI, or mild blood pressure issues.

2. Oral oestrogen (tablet)
Taken daily, but less commonly prescribed due to a slightly higher risk of clot or stroke, and greater fluctuation in hormone levels.

3. Implants or injections
Occasionally used if absorption through the skin is poor, but less widely available.

Body-identical vs synthetic oestrogen

Body-identical oestrogen (also known as bioidentical oestrogen) is chemically identical to the oestrogen your body naturally produces (17β-estradiol).

  • Found in brands like Evorel, Estradot, Oestrogel, Lenzetto, and Sandrena.

  • Supported by NICE and the British Menopause Society as the safest, most effective form.

Synthetic oestrogens, such as conjugated equine oestrogens (CEE, used in older tablets like Premarin or Tibolone), are derived from animal sources and have a different molecular structure.

  • These were common before modern HRT, but are now less favoured due to higher clot and stroke risk.

In short: body-identical oestrogen is modern, safe, and closest to what your body naturally makes.

Progesterone

What progesterone does in the body

Progesterone is produced after ovulation by the ovaries. It balances oestrogen, regulates your cycle, and plays a powerful role in mood, sleep, and brain function.

It also:

  • Protects the uterine lining from thickening when oestrogen is present.

  • Supports calm and sleep by interacting with GABA receptors in the brain (the same ones affected by anti-anxiety medications).

  • Helps regulate blood sugar and fluid balance.

  • Supports thyroid function and immune modulation.

After ovary removal, progesterone production ceases completely. If you still have your womb, you’ll need progesterone in your HRT to protect the endometrium. But even without a womb, some women choose to take it because it can:

  • Improve sleep quality.

  • Reduce anxiety and irritability.

  • Stabilise mood swings.

Replacing progesterone

There are two main ways to replace progesterone:

1. Micronised progesterone (body-identical)

  • The most natural and well-tolerated form, known by the brand name Utrogestan.

  • Usually taken as a capsule (orally or vaginally) for either 12–14 days each month (cyclical) or every day (continuous).

  • Minimal side effects, and may even improve sleep.

2. Synthetic progestogens (known as progestins)

  • Found in older combined HRT tablets or patches (e.g. norethisterone, medroxyprogesterone acetate).

  • Effective but can cause more side effects such as bloating, mood swings, or breast tenderness.

  • Still appropriate for some women if body-identical options aren’t tolerated.

Another option is the Mirena IUS, a hormonal coil that releases progesterone locally into the uterus, providing endometrial protection for up to five years.

Testosterone

What testosterone does in the body

Although often labelled the “male hormone,” testosterone is vital for women too. The ovaries and adrenal glands produce small but powerful amounts that affect:

  • Energy and stamina

  • Cognition, focus, and motivation

  • Sexual desire and pleasure

  • Muscle mass and strength

  • Mood stability and emotional resilience

When the ovaries are removed, testosterone levels fall by roughly half within days. This can lead to symptoms such as:

  • Low libido or loss of sexual sensation

  • Fatigue and low motivation

  • Difficulty concentrating or feeling “flat”

  • Reduced muscle tone or strength

  • Emotional blunting or low mood

Replacing testosterone

Testosterone therapy for women is safe, evidence-based, and recommended by the British Menopause Society for women with low libido or ongoing fatigue despite adequate oestrogen replacement.

In the UK:

  • AndroFeme 1% cream is the only testosterone product licensed for women.

  • Applied daily to the skin (usually the outer thigh, lower abdomen, or buttock).

  • Blood levels should be monitored every 6–12 months to stay within the female physiological range.

Some clinicians prescribe “off-label” testosterone formulations originally designed for men, adjusted to female doses, though AndroFeme ensures a more precise and safer option.

Benefits often appear within a few weeks to months and include better energy, sexual wellbeing, focus, and confidence.

Localised (Vaginal) Oestrogen

Restoring vaginal and urinary health

Even with systemic HRT, the vaginal and urinary tissues can remain dry, sore, or prone to infection due to local oestrogen depletion. Localised oestrogen targets these tissues directly, with minimal systemic absorption.

It’s available as:

  • Creams or gels – e.g. Ovestin or Estriol.

  • Pessaries – small vaginal tablets such as Vagifem.

  • Vaginal rings – e.g. Estring, which slowly releases oestrogen over 3 months.

Used two to three times a week (some women will even use it daily with direction from their GP or menopause specialist), localised oestrogen restores elasticity, reduces irritation, and helps prevent recurrent urinary tract infections. It’s safe to use long-term alongside systemic HRT or on its own if full-body HRT isn’t suitable.

Absorption and dose adjustment

Not every woman absorbs transdermal hormones the same way. Skin thickness, application area, and even individual metabolism can affect blood oestrogen levels.

If you’re still experiencing symptoms despite being on the highest licensed dose, you might be a “poor absorber.” Blood tests can help your clinician tailor your dose — and it’s perfectly safe to combine methods (for example, using both patch and gel) if monitored.

The right HRT should relieve symptoms and restore a sense of balance. If you still don’t feel right, keep advocating for yourself — you deserve treatment that works for your body.