History
How it was actually worked out
2 min read
1672 – 1935
The real explanation arrived in pieces, over two and a half centuries, and mostly from people looking at ovaries rather than at blood.
| Year | What was established | By whom |
|---|---|---|
| 1672 | The corpus luteum clearly described — the yellow structure left in the ovary after a follicle releases its egg. The follicles still carry his name. | Regnier de Graaf |
| 1827 | The mammalian egg identified. Until this point nobody had seen the thing the whole system exists to release. | Karl Ernst von Baer |
| c. 1898–1900 | Proposal that the corpus luteum is a gland of internal secretion acting through the blood, rather than a scar. | Gustav Born; Louis-Auguste Prenant |
| 1903 | Experimental proof of that hypothesis: destroying the corpora lutea in mated rabbits prevented pregnancy. The corpus luteum does something. | Ludwig Fraenkel |
| 1920s | Ovulation timed relative to the next period rather than the last — the luteal phase is the fixed half. Knaus put it at 14 days; Ogino at 12 to 16. | Kyusaku Ogino; Hermann Knaus |
| 1929 | Corpus luteum extract shown to transform the uterine lining and sustain early pregnancy. They named the active substance progestin, for pro-gestation. | George Corner; Willard Allen |
| 1934 | The pure crystalline hormone isolated — by four groups almost simultaneously, in the United States, Switzerland, and two German cities. | Four independent teams |
| 1935 | The competing names unified. It became progesterone. | Allen, Butenandt, Corner, Slotta |
Dates and attributions per the progesterone historical literature and the American Chemical Society record; see sources. Adolf Butenandt, who determined the structure, received the 1939 Nobel Prize in Chemistry for work on the sex steroid hormones.
The sentence the whole page has been building to
Only in 1929 was it established that the bleeding follows the withdrawal of a substance made by the structure left behind after ovulation. Not a purge. Not a surplus. Not a poison. The visible end of a process whose decisive moment happened two weeks earlier and left no visible sign at all.
That is why nobody worked it out sooner. The cause was invisible and the effect was unmissable, so for two millennia the effect was studied as though it were the cause.
What followed immediately
Understanding progesterone made it manufacturable, and manufacture changed everything downstream. Russell Marker's work in the 1940s produced progesterone cheaply from Mexican yam sapogenins; Carl Djerassi's team synthesised an orally active progestin in 1951; the first oral contraceptive was approved in the United States in 1957 for menstrual disorders and in 1960 for contraception. Within thirty years of naming the hormone, the cycle had gone from an unexplained monthly event to something that could be deliberately controlled.
Marker, Djerassi and the approval dates are given here from the standard account of the development of the oral contraceptive and are flagged for verification on the sources list below.