Jason Orendorffjorendorff
Jul 22, 2026, 3:00 PMThe human ovaries have a few hundred thousand follicles, each containing a single egg. But each cycle only one egg is released. Obvious consensus problem. How does the body solve it?
Replies
- Jason OrendorffjorendorffJul 22, 2026, 3:05 PM
It's a race. The pituitary produces FSH, follicle stimulating hormone. Some follicles are activated. They start producing estradiol. That signal causes FSH production to stop.
If FSH drops too early in a follicle's development, it will atrophy and die (via apoptosis, programmed cell death). A follicle that is far enough along when FSH drops becomes the dominant follicle.
https://theluckyegg.com/2023/04/29/dominant-follicle-selection-in-ovulation/
- Jason OrendorffjorendorffJul 22, 2026, 3:24 PM
So the fastest follicle to start developing sends signals that suppress the rest.
The process typically "selects" a single follicle, releasing one egg per cycle. Sometimes the system slips and multiple follicles develop and release eggs; this is how you get fraternal (dizygous) twins.
- Jason OrendorffjorendorffJul 22, 2026, 3:26 PM
How often are multiple eggs released? It depends on timing: relative to the distribution of follicle activations in time, the endocrine signal has to turn around quickly.
If you were engineer-brained enough, without knowing more, you could make an abstract model, estimate the parameters, and simulate this.
It's apparently a normal enough thought that someone did it!
https://www.biorxiv.org/content/10.64898/2026.02.23.707552v1.full
- Jason OrendorffjorendorffJul 22, 2026, 3:37 PM
When I was a kid, I read somewhere that the ratio of twins to single births was something like 1:83, and the ratio of triplets to twins was the same.
I found this really striking. What a coincidence... right?
Well, today I'm not convinced we have numbers as precise as that factoid suggests. But this one mechanism is responsible for like 2/3 of cases of multiple births, and it kinda predicts the proportions would be the same. Each extra dominant follicle is an independent event.
- Jason OrendorffjorendorffJul 22, 2026, 3:39 PM
A bunch of other stuff would have to work out in similar ways, like: each fertilization would also have to be an independent event. (But that makes sense too!)
I got curious this morning and it took me someplace surprising :)