Hello and thank you for your question.
As you may have discovered in your own Internet search, one of the
factors implicated in the decline of free testosterone levels is
excessive binding of testosterone to carrier proteins that divert it
for use in the production of other proteins/hormones, including
estrogen. The therapy that directly addresses this situation is
testosterone replacement, but there is some controversy about whether
testosterone replacement correlates with increased risk of prostate
cancer. Obviously you should consult with a qualified urologist about
whether that route is appropriate for you at this time.
"Testosterone within the circulation is principally bound to proteins,
the most important of which is sex hormone binding globulin (SHBG).
Only about 2 percent of testosterone is unbound (bio-available) and
therefore free to enter cells in order to effect its biological
actions by binding to androgen receptors...."
"Hypotestosteronaemia levels [that is, low levels] quoted in papers
vary between around 300 ng/dl (10.4 nmol/L) and 400 ng/dl (13.9
HYPOGONADISM - WHAT IS A LOW LEVEL OF TESTOSTERONE?
"Bioavailable testosterone refers to the 'free' portion of the hormone
unbound to carrier proteins which is able to act directly upon target
Sexual Dysfunction and Male Hormones
"It is well known that androgen levels decline in men with age.
Furthermore, as a result of the increase in binding capacity for
testosterone in serum, there is an early and more dramatic decline in
free testosterone, the physiologically functioning component of serum
testosterone, than in the total testosterone concentration...."
"The ideal therapy should consist of creating physiologic testosterone
concentrations (400 to 700 ng/dL in blood taken in the morning) and
restoring circadian variations."
Hormone Replacement Therapy for Aging Men
Since your score is higher than the 300-to-400 range that normally
merits treatment, you are still within the 'normal' range, albeit at
the low end of it. So you should look before you leap into a course
The following article talks about estrogen conversion and hormone
replacement, but I think it's a bit over-entusiastic in its promotion
of the treatment:
MALE HORMONE MODULATION THERAPY
Not to scare you, but here's one more thing that you should be aware
"Of great interest is a recent finding that men with coronary artery
disease have significantly lower levels of plasma testosterone than
controls and that intracoronarv testosterone infusion in men with
coronary artery disease increases coronary blood flow. Such findings
suggest that age related declines in testosterone in men may be
associated with heart disease ...."
So besides discussing hormone replacement with a urologist, if you
haven't had a general physical in the last few years you should do
Search terms used:
free testosterone serum decline
I hope you find this information useful and responsive to your
question. Of course you should not consider this answer as medical
advice (and I'm not a physician).
Clarification of Answer by
14 Oct 2002 15:42 PDT
I think it's best to look at the serum testosterone and free
testosterone figures separately.
You report serum testosterone of 452, free testosterone of 18.17, and
18.17/452 = 4.02% free.
The reference range for serum testosterone is 241-827 (this source
says 350-1030 with a mean of 627 over ages 20-50); the reference range
for free testosterone is 5-21 (this source says 5.2-28); and the
reference ratio is 1-2.7 (this source says 1.5-3.2).
I really think you shouldn't worry about the ratio. True, your serum
number is a little on the low side and your free number is a little on
the high side. But to say your ratio is twice as high as normal
exaggerates the effect. Here's an arithmetical example. Say a ratio
of 2.5% is 'normal', and arises from a ratio of 12.5/500. If you
couple a 30% increase to the numerator with a 30% decrease to the
denominator, the fraction becomes 16.25/350 or about 4.6%.
So there's nothing unusual about your numbers. As for your symptoms,
a visit to a urologist would still be a good idea.