If you have ever wondered:

“How is testosterone produced in men?”

(or)

“What is the HPA & HPG Axis”

Then this succinct guide is for you.

Let’s get started.

Definition #1 The Hypothalamic Pituitary Adrenal (HPA) Axis

It is an endocrine pathway made up of the hypothalamus, the pituitary gland, and the adrenal gland. It is an integral part of the testosterone production process.

Definition #2 The Hypothalamic Pituitary Gonadal (HPG) Axis

It is an endocrine pathway made up of the hypothalamus, pituitary gland, and gonadal glands. It is the second part of the testosterone production cycle.

How The HPA & HPG Axis Make Testosterone In Men

Step 1 Hypothalamus

Testosterone production starts in the brain.

The release of gonadotropin-releasing hormone (GnRH) is regulated by the hypothalamus.

The hypothalamus receives signals from other hormones circulating in the body that tell it to increase or decrease the production of GnRH.⁽¹⁾

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Step 2 Anterior Pituitary

GnRH travels (a short distance) down to the anterior pituitary which releases luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

LH and FSH are then released into circulation throughout the body.

Step 3a Testes

LH eventually finds its way to the testes. Once in the testes, it binds to leydig cells.

Leydig cells increase the production of a protein called steroidogenic acute regulatory protein (StAR).

StAR helps move cholesterol into the mitochondria.

Step 3a Testes Pathway 1

Once cholesterol is inside the inner mitochondrial membrane, it is converted to pregnenolone and this starts the process of creating testosterone.

Pregnenolone is converted to 17α-Hydroxypregnenolone.

17α-Hydroxypregnenolone is converted to dehydroepiandrosterone (DHEA).

DHEA is converted to Androstenedione.

Finally, Androstenedione is converted to Testosterone.

Step 3a Testes Pathway 2

Once cholesterol is inside the inner mitochondrial membrane, it is converted to progesterone and this starts the process of creating testosterone.

Progesterone is converted to 17α-Hydroxypregnenolone.

17α-Hydroxypregnenolone is converted to Androstenedione.

Finally, Androstenedione is converted to Testosterone.

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Step 3b Adrenal Glands

Another way testosterone is created is from the adrenal glands, but not directly.⁽¹⁾

The adrenal glands produce several prohormones that are converted into testosterone peripherally.⁽¹⁾⁽¹⁾

These prohormones include:

• Dehydroepiandrosterone (DHEA)
• Dehydroepiandrosterone sulfate (DHEAS)
• Androstenedione (A4)
• Androstenediol (Α5)
• 11β-hydroxyandrostenedione (11βOHA4)

Production And Regulation Of Testosterone

Testosterone limits its own secretion via a negative feedback loop.

An increased level of testosterone in the blood sends feedback to the hypothalamus that it should suppress the secretion of GnRH. It also sends feedback to the anterior pituitary telling it to be less responsive to GnRH.⁽¹⁾

Key Takeaways

Testosterone production in men is complex.

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After reading today’s guide you should have a better understanding of how testosterone is made.

Using this information, you can pinpoint different areas in the process that may be impacting your own testosterone levels.

If you are interested in learning more about the unique T-boosting framework used here at AndrogenHacker, it takes less than 30 seconds to fill out the form below.

Thanks for reading. 🙂

David, RN, CCRN