Progesterone: a hormone whose best-known effect in this context is sleep

A reproductive hormone with a second life as a neurosteroid. The reason it makes people sleepy is a real metabolic pathway, and it is also the reason the route it is taken by changes what it does.

Two different molecules doing two different jobs

Established clinical use Progesterone acts at the progesterone receptor — the reproductive role, and in hormone therapy the reason it is given alongside oestrogen to protect the endometrium. It is also converted by 5-alpha reductase and 3-alpha hydroxysteroid dehydrogenase to allopregnanolone, which is not a sex hormone at all: it is a positive allosteric modulator at the GABA-A receptor, the same site benzodiazepines act on.

That second pathway is where the sedation, the anxiolytic effect and the sleep improvement come from, and it explains a practical detail that otherwise looks arbitrary. Oral progesterone passes through the liver first, where much of that conversion happens, so the oral route produces markedly more allopregnanolone than a transdermal or vaginal one. Taking it orally at night is not a convenience; it is how you get the neurosteroid effect. Vaginal delivery targets the uterus and largely bypasses it.

Established clinical use Synthetic progestins are not this molecule. Medroxyprogesterone and the others bind the progesterone receptor but are not substrates for the same conversion, so they do not produce allopregnanolone, and their cardiovascular and breast signals in the large hormone therapy trials are not interchangeable with bioidentical progesterone’s. Conflating the two is the most common error made about this hormone.

Where it is used, and how well established each use is

Established clinical use The approved use is the solid one: in women taking oestrogen with a uterus, progesterone opposes endometrial proliferation, and that is not optional. It is also used in fertility treatment and in pregnancy support.

Off-label or community practice Use for sleep, in women and men, rests on the allopregnanolone mechanism and on small studies rather than on large trials. It is plausible, widely practised, and not established. The low topical amounts the app records for men are further out still — the rationale is that progesterone modestly inhibits 5-alpha reductase and so moderates DHT, and there is very little human data behind using it that way.

Anyone whose actual problem is sleep should know that the boring interventions have stronger evidence than any hormone: cognitive behavioural therapy for insomnia outperforms hypnotics in trials and keeps working afterwards, and sleep apnoea, thyroid disease and medication effects are worth excluding first.

What to watch

Sedation is the effect people notice, which is why it is taken at night and why driving the next morning is worth a thought during the first week. Bloating, breast tenderness and mood changes are the common complaints, and they are dose-related.

The app’s panel is a hormone panel — serum progesterone, estradiol, SHBG, with breast examination and cervical screening for women, and a full hormone panel in men. Serum progesterone is worth a caveat: it fluctuates enormously across the menstrual cycle and after an oral dose, so a single value without a stated timing is difficult to place, much like T3.

Whether this applies to a particular person, in what form and by what route, is a prescribing decision, and anything on the drawbacks list below belongs with the clinician who makes it.

The dosing rows the app records

Off-label or community practice Reproduced from the app’s reference so you can see what it holds, not as a recommendation. Which row applies to a particular person, if any, is a clinical decision this page does not make — and rows describing supraphysiological or post-cycle use are filtered out before this table is built, so what you see here is a subset.

What the app monitors alongside it

The panel below is the app’s own monitoring note for Progesterone, verbatim. The analytes in it that have a page here are linked; those pages cover what each one measures, which assay produced it and how to read a trend.

• Sensitive versus standard estradiol
• Free versus total testosterone, and the three ways labs get the free number
• SHBG
• Hematocrit on testosterone therapy

Drawbacks and risks the app records

From the app’s own entry, and the third item is the important one: bioidentical progesterone and the synthetic progestins are not the same drug and do not share evidence.

• Sedating — must be used at night for most
• Can cause bloating and breast tenderness
• Synthetic progestins have different effects — bioidentical preferred
• Weight gain in some users
• Progesterone creams have variable absorption

Questions people actually ask

Why take it at night?

Because oral progesterone is converted on first pass through the liver to allopregnanolone, which acts on GABA-A receptors and is sedating. Taking it at night uses that rather than fighting it.

Is a progesterone cream equivalent to a capsule?

Not for the neurosteroid effect. Transdermal delivery bypasses the first-pass conversion that produces allopregnanolone, and cream absorption is variable. For endometrial protection the route matters differently again — that is a prescriber’s call.

Are progestins the same thing?

No. Synthetic progestins bind the same receptor but are not converted to allopregnanolone, and their trial data on cardiovascular and breast outcomes does not transfer to bioidentical progesterone.

Does it help men?

The rationale is modest 5-alpha reductase inhibition and the sleep effect, and the human data behind using it that way is very thin. The app records low topical amounts with a three-month reassessment, which is an appropriately cautious framing for something this unstudied.

Where the load-bearing numbers come from

Named rather than linked. Publisher URLs move, and a citation that resolves to a 404 two years from now is worse than one you can search for by name — every entry below is findable from the title and year alone.