Ech_01 t1_j76ntwz wrote on February 4, 2023 at 2:16 PM

Reply to comment by jacknikedisamotracia in What causes the onset of puberty specifically? by Voomit

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.

_AlreadyTaken_ t1_j78srhe wrote on February 4, 2023 at 11:20 PM

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.

Ech_01 t1_j78v8jv wrote on February 4, 2023 at 11:39 PM

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

_AlreadyTaken_ t1_j7bk0hu wrote on February 5, 2023 at 4:04 PM

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.