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Not medical advice. The Atlas is not a substitute for a clinician who can examine you.

The Steroidogenic Enzyme Cascade

3beta-HSD, CYP17A1, and 17beta-HSD, cholesterol to testosterone

Evidence grade 4 of 5, Strong. Read how the Atlas grades evidence.

The written rationale for this grade is still being prepared.

FDA
Not applicable (physiology)

Reference only. Not medical advice.

This is something to take to a clinician. The Atlas can tell you what is known about the steroidogenic enzyme cascade in general. It cannot tell you what is happening in your body, and the difference matters most for exactly the symptoms that bring people to this page.

Once CYP11A1 makes pregnenolone, a cascade of enzymes finishes testosterone. CYP17A1 performs two jobs (17-alpha-hydroxylase and 17,20-lyase), 3-beta-hydroxysteroid dehydrogenase (3beta-HSD) converts delta-5 to delta-4 steroids, and 17-beta-HSD (type 3) performs the final step to testosterone. The path runs pregnenolone to DHEA/androstenedione to testosterone. Understanding this cascade clarifies where downstream conversions branch off: 5-alpha-reductase makes DHT, and aromatase (CYP19A1) makes estradiol.

The four-enzyme assembly line from pregnenolone to testosterone.

What it is invoked to explain

Claims this idea is used to support. Whether it supports them is the rest of the entry.

  • Maps the precursor pathway behind 'pro-hormone' supplements

How it works

Pregnenolone is processed through 3beta-HSD and CYP17A1's hydroxylase and lyase activities to androstenedione, then reduced by 17beta-HSD type 3 to testosterone in the Leydig cell. Adrenal androgens (DHEA, androstenedione) feed the same downstream enzymes peripherally, which is why DHEA is sometimes marketed as a testosterone precursor, though in men with normal gonadal function it rarely raises testosterone.

What people get wrong

  • Often saidTaking a precursor (DHEA, androstenedione) reliably raises testosterone

    ActuallyThe enzymes are tightly regulated; in men with normal testes, supplemental precursors are largely shunted or aromatized rather than reliably raising serum testosterone.

Who profits, and who pushes back

Nobody is named here yet, because we have not done that work on this entry. Read that as unfinished. Somebody almost certainly sells this, and somebody almost certainly disputes it. Assume both until we have checked.

At a glance

Bifunctional enzyme
CYP17A1 (hydroxylase + lyase)
Final step
17beta-HSD type 3 -> testosterone
Branches
5-AR -> DHT; aromatase -> estradiol

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about The Steroidogenic Enzyme Cascade. A short entry is not a safe entry.

  • Timeline. We have not built the dated record of research and regulatory events.
  • Cost and market. We have not documented what it sells for or who sells it.
  • Supply chain. We have not mapped where it is made.
  • Who uses it. We have not documented the user groups.
  • What could change. No forward-looking summary yet.
  • How it compares. We have not set it against the alternatives.
  • Children and teenagers. We have not checked what is known about younger people.
  • What can go wrong. We have not written the risk line for this one. Read the safety section below rather than treating its absence as reassurance.
  • Where we land. We have not taken a position on this yet.

Sources

No sources recorded for this entry yet. Nothing on this page can be checked against a citation until that changes, so treat it as a summary awaiting its evidence.