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Ech_01 t1_j76mea4 wrote

GNRH release is regulated by KNDY-neurons (Kisspeptide-neurokinine B -dynorphine)

The KDNY neurons get stimulated by progesteron, we get release of Kisspeptide which stimulates the GNRH neuron and releases GNRH

GnRH then binds on the gonadotropic cells which causes the release of FSH and LHLH and FSH stimulate the production of testosteron and estrogen then inhibits the KDNy-neurons (negative feedback loop) so we don't get too much of GNRH release

Edit: I don't exactly know what causes this release in the first place, but studies have shown that leptine, a hormone secreted by fat cells in the human body, stimulate the KNDY-neurones which could lead to the start of the GnRH release.

During puberty (10-12yo) the child starts having lots of lipid cells which thus means more leptin secretion. This also means the "fatter" childeren get a faster puberty. It's a process called the gonadarche.

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source: med student

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StinkyBrittches t1_j76nqj8 wrote

If I've learned to extrapolate anything from BioChem, there's probably a gonadotropin releasing hormone releasing hormone.

And also a gonadotropin releasing hormone releasing hormone releasing hormone.

It's releasing hormones all the way down.

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Ech_01 t1_j76o9sa wrote

Haha it's crazy how the body is made. This hormone produces this which produces this which produces this x100

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rogert2 t1_j77bw6e wrote

There are several things in biology that function as fuses. Sometimes, one fuse lights another; one benefit of having such a "fuse junction" is that it can serve as a checkpoint that can trigger several things.

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-Metacelsus- t1_j77hggg wrote

Interestingly, age of female puberty has been steadily decreasing over the last century. https://pubmed.ncbi.nlm.nih.gov/12319855/ https://vitalrecord.tamhsc.edu/decreasing-age-puberty/

This is probably due to increasing food consumption.

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3leberkaasSemmeln t1_j77x4ju wrote

Makes sense from evolutionary point of view. Oh there is enough food? Then we can go into this major growth, that requires a lot of energy. Oh there is not enough food? Let’s wait another year or two and hope that the situation is better then.

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TwentyCharactersShor t1_j77rppu wrote

Decent answer :)

The only thing I'd add (and I'm simplifying a lot here) is that if you imagine that the cells in the body are constantly signalling to each other, at various tipping points, one (or more) signal becomes more dominant than the other which in turn can trigger new behaviours.

So, the absolute trigger isn't often evident as it is the result of systemic change in cell function.

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scarf_spheal t1_j77ujav wrote

This was what i learned concerning this topic. The rate of producing the hormone was just slightly higher than the clear rate. Eventually it hits the concentration tipping point and begins the process. I vaguely remember it relating to how puberty starts, but it was so long ago I learned it the field probably moved to a different or more accurate understanding

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jacknikedisamotracia t1_j76mz5v wrote

and what causes the high release of progesteron in first place?

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Ech_01 t1_j76ntwz wrote

Well if you want more detail, while the fetus is in the placenta (a place where lots of estrogen is located), we get inhibition of the KDNy neurons. (see above)

After birth, the high [] of estrogen that came from the mother goes away, so the KDNy neurons start releasing Kiss peptide => stimulation of the GnRH-neuron => LH and FSH release => testosteron + estrogen production

LH stimulates the production of progesteron and other androgens which leads to a positive effect on this cycle.

After 3 months the GABA hormone concentration starts getting high enough to block the KDNy neuron activity => the LH and FSH production (and testosteron as well) stops from the age of 6months until the age of 10 years old, where leptine starts getting produced as well and we get a more positive feedback on the testosteron production.

Edit: something like this

I also wanna say many other hormones play a role, but to keep it simple I only mentioned the important ones.

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_AlreadyTaken_ t1_j78srhe wrote

This is the first time I've seen an answer that wasn't just a mechanism description (estrogen or testosterone get produced!). No one would say why it starts in the first place and why it tends to occur around a certain age range.

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Ech_01 t1_j78v8jv wrote

Yeah I mean lots of people know the basics about these hormones, but relatively few know the details. Glad I could help.

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_AlreadyTaken_ t1_j7bk0hu wrote

I've been fascinated by fetal development and cellular signaling and it is brutally complex when you get down to the level of cellular receptors and signaling cascade chains, dna expression, etc. You have signals signaling signals, hormonal triggers, electrolyte triggers (i.e. calcium) and multiple pathways, feedback loops, etc. I'm amazed these all function and we are alive when you look at it all.

I wonder how many of these systems are really necessary and just reflect the random progression of evolution or do they represent a hardiness that comes from redundancy?

To develop medications that work on one of these pathways is a huge challenge. You'd not only have to track the ramifications of modifying the pathway but how all the other ones and various feedback systems would respond in kind. On top of that you can have the same receptors and signaling proteins used for different systems around the body, they are only differentiated by cell type and physical isolation (diffusion limits), so you can't just pump a drug into the blood stream without affecting "innocent bystanders" (i.e. serotonin drugs).

One more thing, it is amazing how much is controlled by the hypothalamus and brain stem, the most primitive parts of the brain. It must reflect its early origins and how basic these systems are. The cerebellum and cerebrum, by virtue of their external physical locations, can grow or modify more freely without much limitation but the hypothalamus and related structures, have to pretty much stay constant in their basic structure and functions. It is surprising to see that a cluster of neurons (KNDy) would be behind this process but I really shouldn't be. It is no coincidence the pituitary is so closely linked physically and chemically to that region.

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TheMooseIsBlue t1_j796zmh wrote

This is like a game of wack-a-mole. One thing is triggered by another, which was triggered by another, but we still can’t seem to get to the why. I interpret OP’s question to be “why does it start at the age it does,” so why doesn’t this cause and effect chain start at like age 5 or age 20 or age 50?

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Ech_01 t1_j7acdbt wrote

Like i said in my comment above, leptin hormone starts spiking during the age of 10 which releases the inhibition on KDNy-neurons and thus we get release of Kiss peptides, thus GnRH starts getting released and we get FSH and LH (thus Testosterone)

Check my other comment in this thread for more detail

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