Progesterone

Progesterone is a hormone that plays a key role in the menstrual cycle and pregnancy. After ovulation, progesterone levels rise to prepare the uterus lining for a possible pregnancy. If no pregnancy happens, progesterone drops — and that drop is what triggers your period. A synthetic version called progestogen is used in most types of hormonal contraception.

• Progesterone is a hormone produced mainly by the ovaries after ovulation.
• It prepares and maintains the uterus lining for pregnancy.
• When progesterone drops at the end of the cycle, the lining sheds — that's your period.
• Synthetic progesterone (progestogen) is used in the pill, implant, injection, IUS, and other contraception.
• It also plays a role in PMS symptoms — the drop in progesterone before your period is part of why you might feel moody, tired, or emotional.

[DIAGRAM: Infographic showing what progesterone does — role in menstrual cycle, pregnancy, and hormonal contraception]

What it does in the menstrual cycle

Progesterone is the dominant hormone in the second half of the menstrual cycle (the luteal phase — roughly days 15-28). After ovulation, the empty follicle in the ovary transforms into something called the corpus luteum, which pumps out progesterone.

This progesterone does a few things: it maintains the thickened uterus lining that oestrogen built up in the first half of the cycle, it makes the lining more "sticky" and blood-rich (ready for a fertilised egg to implant), and it thickens cervical mucus to create a kind of plug. If a fertilised egg implants, progesterone stays high to support the early pregnancy. If it doesn't, the corpus luteum breaks down, progesterone drops sharply, and the lining sheds as a period.

That progesterone drop is also why many people experience PMS symptoms in the days before their period — mood changes, irritability, tiredness, breast tenderness, and bloating are all linked to falling progesterone levels.

Progesterone vs progestogen

You'll see both words around contraception, and they're related but different:

• Progesterone is the natural hormone your body produces.
• Progestogen is the synthetic (man-made) version used in contraception and other medications. It mimics what progesterone does.

Most hormonal contraception contains progestogen — either alone (progestogen-only pill, implant, injection, IUS) or combined with oestrogen (combined pill, patch, vaginal ring). The progestogen in contraception works by thickening cervical mucus (blocking sperm), thinning the uterus lining, and in many cases suppressing ovulation.

Progesterone and mood

The link between progesterone and mood is real. In the second half of the cycle, when progesterone is high, some people feel calmer but also more tired or sluggish. When it drops sharply before a period, mood can dip — this is one of the main hormonal drivers of PMS.

This is also relevant to hormonal contraception. Because progestogen-only methods keep progestogen levels more constant (rather than following the natural rise and fall), some people find their mood evens out. Others find the constant progestogen affects their mood negatively. Responses to hormonal contraception vary a lot from person to person, which is why trying different methods until you find one that suits you is a normal part of the process.

Things people get wrong

"Progesterone and progestogen are the same thing." They're closely related, but progesterone is the natural hormone and progestogen is the synthetic version. They behave similarly but aren't identical.

"Progesterone only matters during pregnancy." It's active every menstrual cycle, whether pregnancy happens or not. It's also central to how most hormonal contraception works.

"PMS is all in your head." PMS symptoms are driven by real hormonal changes — specifically the drop in progesterone (and oestrogen) before a period. The symptoms are physical and emotional, and they're not imagined.

Things people ask about progesterone

Why do I feel so different in the second half of my cycle?

Because progesterone is the dominant hormone during that phase. It can make you feel sleepier, more emotional, bloated, or experience breast tenderness. When it drops before your period, you might feel a mood dip. This is your body's hormonal pattern — it's real and normal.

Does hormonal contraception replace my natural progesterone?

Progestogen-only contraception provides a steady level of synthetic progestogen, which overrides parts of your natural cycle. Your ovaries may still produce some natural progesterone, but the synthetic version is doing the heavy lifting in terms of preventing pregnancy.

Can I do anything about PMS caused by progesterone changes?

Regular exercise, enough sleep, balanced eating, and managing stress can all help. For more severe PMS (sometimes called PMDD — premenstrual dysphoric disorder), a GP can discuss options including hormonal treatment and medication. [CHECK: current NICE guidance on PMDD management]

Progesterone is a hormone made by the body, mainly after an egg is released each month. Its job is to get the womb ready in case a pregnancy starts. It keeps the soft lining inside the womb thick and ready.

If no pregnancy happens, the body stops making as much progesterone. When the levels drop, the lining comes away. That's what causes a period.

This drop in progesterone is also part of why some people feel moody, tired, bloated, or emotional in the days before their period. Those feelings are caused by a real change in hormones, not by imagining things.

A man-made version of progesterone, called progestogen, is used in lots of types of birth control. The implant, the injection, some types of pill, and the hormonal coil all use it. It works by thickening the mucus inside the body so sperm can't get through, thinning the lining of the womb, and in many cases stopping an egg from being released.

Different people react differently to progestogen. Some feel fine on it. Some find it affects their mood. If one type of birth control doesn't suit you, a different one might work better.