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Encore: Testosterone breakthrough


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Jim Marshall (not a doctor) said ...

There has been much discussion lately on this forum, and on our teleconferences, on the topic of testosterone.

The hormone treatments we have for prostate cancer work by stopping the testosterone being used by the prostate cancer cells to grow.

The first, and strongest, part of hormone treatment is to reduce the testosterone being made by your testes (balls).

When it works, and your testosterone is low enough, it is said to be at castrate levels.

If testosterone fails to go to castrate levels, or jumps above castrate levels for some time, this is called testosterone breakthrough.

In a study of 2196 men, testosterone breakthrough was reported in 3.4% or 6.6% of men (at FDA levels or PSA suppression levels, see How low? below).

The hormone treatment to reduce the testosterone from your testes is most usually by in injection of an implant every 1, 3 or 6 months. Most usually this is an LHRH agonist (like Zoladex, Lupron, Eligard) or occasionally an LHRH antagonist (Abarelix, Firmagon (degarelix)).

These drugs were initially approved for use in the USA by their Federal Drugs Administration (FDA).

The FDA, in their approvals give prescribing guidelines for doctors who use them.

The prescribing guidelines for all FDA-approved LHRH agonists and antagonists recommend monitoring testosterone levels to ensure that castrate level is maintained.

But the guidelines do not say when, or how often:

  • Some doctors measure testosterone with every PSA test to be sure.
  • Some doctors measure testosterone only after PSA goes up, to check that castrate levels are really achieved.
  • Some doctors (in USA) are reported to never measure testosterone of patients on hormone treatment.

Two factors make it harder to understand the issue.

  • How low should testosterone go to be considered castrate?
  • As in miles/kilometres, the measurement may be in ng/dL (often in USA) or nmol/L (often in Australia).

How low?

  • The level considered castrate by the FDA when approving the drugs (less than 50 ng/dL or 1.7 nmol/L).
  • The level above which PSA is not suppressed (less than 32 ng/dL or 1.1 nmol/L)
  • The level which happens with surgical castration (orchiectomy) (less than 20 ng/dL or 0.694 nmol/L)

So, the topic we are encoring today is the one on Testosterone Breakthrough which you can read on our website at:


See recent discussion on this topic started by Guihan at Who would be interested in a case like mine?



... end Jim

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