The HPTA and Androgens PART 2
Cholesterol is converted into testosterone by something called the Leydig
Cells, which (in men) are located in the testes. To do this, 2 enzymes
(cytochrome P450 and 3 and 17 ß-hydroxysteroid dehydrogenases) are
required, in addition to cholesterol. When these enzymes interact with
cholesterol, they can form Testosterone in your body. Then, after
testosterone is produced it can elicit a variety of anabolic and androgenic
effects. As previously stated, this is a good thing, because the more
testosterone you have circulating, the more muscular you will likely be. So
now that we have covered where testosterone comes from, how does the
body actually receive the signal to release it from the testes?
At the age of puberty, Gonadatropin Releasing Hormone (GnRH) is released
in increasingly large amounts from the Hypothalamus, in turn causing the
secretion of Follicle Stimulating Hormone (FSH) and Luteinizing Hormone
(LH) from the pituitary, and finally the male gonads (testes) are stimulated
by those pituitary hormones (LH and FSH). This in turn causes the release of
testosterone (which was produced from cholesterol) into the body.
FSH, although formerly thought to only have a role in production of sperm,
actually aids the in regulation of Leydig Cell function, while LH directly
aids the Leydig Cells in the testes to synthesize testosterone from cholesterol
and thereafter secrete it. The synthesis and subsequent secretion of
testosterone then causes a surge in other anabolic hormones such as Insulin
Like Growth Factor and Growth Hormone. Simple enough, right?
Oh yeah…I also mentioned something called “Dihydrotestosterone” if you
recall. Well, this is actually more androgenic than testosterone, though less
anabolic. It is created within the body by an enzyme called 5-alpha
reductase. All of this sounds great, right? The body is a testosterone
producing machine! Well, it’s not all roses. Remember how your body likes
to maintain itself in a way so as to be evolutionarily sound? Well, obviously,
if it creates too much testosterone, it’s not going to be able to survive a
famine (as it will have too much muscle and not enough fat), so it makes use
of something called the “negative feedback loop”.
So, once testosterone is created it has the ability to in turn to undergo various
metabolic processes that will inhibit GnRH, which in turn inhibits the
secretion of LH and FSH, and that brings a halt to natural testosterone
production. This is the negative feedback loop.
One of those metabolic processes is called “aromatization”. This is the
conversion of testosterone into Estrogen via the aromatase enzyme. And
guess what? The more estrogen you have in your body, the less muscular
and more fat you’re going to be. Think of it as the hormonal opposite of
testosterone.
The production of estrogen as well as other factors all add up to put a halt to
the production of testosterone as well hindering our body transformation
efforts. And once testosterone has stopped being produced, it no longer
converts to the hormones which send the negative feedback signal, and
GnRH eventually begins to do its job again when it senses the need for more
testosterone. In this way, your body prevents excess hormones from being
secreted and thus maintains homeostasis- the dreaded status quo.
So now we know that we want some testosterone (as much as possible)
floating around, but how does it actually do what it does?
Well, testosterone (or any natural as well as synthetic androgen) operates by binding the androgen receptor (AR). Once it binds, it travels to the cell’s nucleus along with another Androgen/Receptor coupling, and initiates its various effects.
Once the androgen arrives in the nucleus, it begins a process known as “gene transcription” which basically means that it delivers a message to your cells. The message can be a variety of things, build more muscle or burn more fat
(i.e. transform my body!).
