Progesterone
Also called: the cycle hormone, luteal hormone
Progesterone is a sex hormone produced mainly by the corpus luteum in the second half of the menstrual cycle and by the placenta in pregnancy. It prepares the uterine lining for pregnancy, supports sleep, and slows gut motility. Levels drop sharply if pregnancy does not happen, triggering a period and many of the PMS symptoms women feel in the last week of their cycle.
What progesterone does in the body
- Prepares the uterine lining (endometrium) for implantation.
- Stabilises pregnancy when implantation happens.
- Slows gut motility (bloating and constipation in the luteal phase).
- Acts as a mild anti-mineralocorticoid (competes with aldosterone), prompting a compensatory rise in aldosterone.
- Raises body temperature about 0.3 to 0.5 C after ovulation.
- Has mildly sedating, GABA-like effects in the brain (helps sleep early in the luteal phase).
- Modulates immune function (mildly immune-suppressing in pregnancy).
When and how it changes
- Follicular phase (week 1-2 of cycle): low.
- After ovulation: rises sharply.
- Luteal phase (week 3-4): high.
- Late luteal (last 5-7 days): falls if no pregnancy. Drop triggers period and PMS.
- Pregnancy: rises continuously, peaks at 100 to 200 ng/mL late in pregnancy.
- Perimenopause: erratic, often with anovulatory cycles where progesterone barely rises.
- Post-menopause: very low and stable.
- Hormonal contraception (most types): suppresses natural cycle, replaces with synthetic progestin.
How progesterone affects the gut
Progesterone receptors are widespread in the gastrointestinal tract. High progesterone slows transit by about a day on average. and slows gastric and colonic muscle contraction directly. This is why bloating, constipation, and food sensitivity reactions tend to cluster in the second half of the cycle. They are predictable, not random, and they ease once bleeding is established.
Low progesterone, when it matters
- Short luteal phase (10 days or less) is linked to lower progesterone and a thinner lining, though it has not been proven to independently cause infertility.
- Anovulatory cycles in perimenopause: progesterone never rises, oestrogen unopposed, sometimes very heavy bleeding.
- Diagnosis: blood test on day 21 of a 28-day cycle (timing matters).
- Treatment: bioidentical progesterone (Utrogestan) or synthetic progestins, typically prescribed in perimenopause as part of HRT, or in fertility care.
Progesterone for sleep
Many women in perimenopause find that adding bedtime progesterone (Utrogestan 100 to 200 mg) improves sleep. The effect is real for some, progesterone metabolises into allopregnanolone, which acts on GABA receptors. Effect varies; some feel groggy, others sleep noticeably better. It is part of standard HRT for women with a uterus and is not yet routinely prescribed for sleep alone.
Common questions
- Why am I more bloated after ovulation?
- Rising progesterone slows gut motility and increases water retention. Bloating builds in the late luteal phase, but self-reported fluid retention actually peaks on the first day of bleeding, not premenstrually. It is hormonal, predictable, and not a food problem.
- Can I take progesterone for sleep?
- Yes if you are perimenopausal or post-menopausal and have a uterus. Bedtime Utrogestan 100 to 200 mg is part of standard HRT and many women find sleep improves. Not a recreational sleep aid; needs prescriber oversight.
- Is progesterone the same as progestin?
- No. Progesterone is the body's natural hormone (also available as bioidentical Utrogestan). Progestins are synthetic versions used in some contraception and older HRT. Effects overlap but are not identical.
- Does progesterone cause weight gain?
- Mostly not. The luteal-phase weight increase most women see is water retention (1 to 3 kg), which clears within 2 days of bleeding. Long-term progestin contraception is associated with mild weight gain in some users; bioidentical progesterone is generally weight-neutral.
Sources
- Fluid Retention over the Menstrual Cycle, White et al 2011 (International Journal of Endocrinology (PMC3154522))
- Effects of Gender and Menstrual Cycle on Colonic Transit Time in Healthy Subjects, Kim et al 2013 (Korean Journal of Internal Medicine (PMC4531623))
- Progesterone induces changes in sleep comparable to agonistic GABA-A receptor modulators, Friess et al 1997 (American Journal of Physiology (PMID 8897866))
- Temperature regulation in women: Effects of the menstrual cycle, Charkoudian & Stachenfeld 2020 (Temperature (PMC7575238))
- The role of sex hormones in aldosterone biosynthesis and the mineralocorticoid receptor (progesterone as anti-mineralocorticoid) (Cardiovascular Endocrinology & Metabolism (PMC11155591))
- Progesterone Inhibitory Role on Gastrointestinal Motility (Physiological Research (PMC9150547))
- Sex hormones in the modulation of irritable bowel syndrome (visceral sensitivity peaks when hormones are low) (World Journal of Gastroenterology (PMC3949254))
- Serum progesterone and PIBF across trimesters in healthy pregnant women, Hudic et al 2020 (Journal of Reproductive Immunology (PMC7051977))
- Anovulatory Bleeding (unopposed oestrogen in anovulatory perimenopausal cycles), StatPearls (StatPearls, NCBI Bookshelf)
- Diagnosis and treatment of luteal phase deficiency: a committee opinion (2021) (American Society for Reproductive Medicine (ASRM))
- Progesterone (ovulatory test): mid-luteal day 21 timing (GPnotebook)
- Utrogestan (micronised progesterone) explained: bedtime sedative dosing and endometrial protection (Newson Health / Dr Louise Newson)
- Progestin-only contraceptives: effects on weight (Cochrane review summary), Lopez et al (American Family Physician (PMC4646426))
- Progesterone and its metabolites in affect regulation in the female brain (International Journal of Molecular Sciences (PMC10143192))