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2014; 60(4):286-294
in levels considered as the gold standard for free testos-
terone level. The normal value of this method in men is
131 to 640 pmol/L
31
(
D
).
As weekly variations can occur in testosterone, espe-
cially in older men whose levels of testosterone fluctuate
between lower and normal limits, at least two testostero-
ne measurements should be made to confirm the diagno-
sis of hypogonadism
18
(
A
).
Recommendation
The diagnosis of LOH is based on clinical aspects of hypo-
gonadism and demonstration of morning serum levels
of total and free testosterone below the minimum refe-
rence value for healthy young adults. The laboratory de-
finition of LOH has not yet been established.
W
hat
is
the
role
of
salivary
testosterone
levels
?
The measurement of hormones using saliva is easy and
noninvasive.
It is believed that for various hormones the concen-
trations in saliva represent the concentration of forms un-
bound to protein in the blood. Landman et al. demons-
trated the presence of testosterone in saliva in 1976, and
this fact was confirmed by various other studies. One re-
cent study conducted with 144 men between 20 and 89
years old demonstrated that salivary testosterone (ST)
correlates with TT (total testosterone), FTc (calculated
free testosterone) and BAT (bioavailable testosterone).
This fact adds to the previous literature demonstrating
that ST is correlated with free testosterone using dialy-
sis. A circadian rhythm was observed in ST similar to that
observed in serum testosterone levels. The data from the
study confirmed the validity of the determination of ST
as a measurement that evaluates bioavailable testostero-
ne. The, study was the largest to confirm the decrease of
ST with male aging. It demonstrated a good correlation
with the symptoms of late-onset hypogonadism evalua-
ted using the ADAM test
32
(
B
).
It was demonstrated that the level of ST is a reliable
option for the measurement of free testosterone, but as
yet cannot be recommended for generalized use becau-
se the methodology has not been standardized, and the
ranges for adult men are not available at the majority of
hospitals and reference laboratories
30
(
B
).
Recommendation
It was demonstrated that the level of ST is a reliable subs-
titute for the measurement of free testosterone, but as
yet it cannot be recommended for generalized use becau-
se the methodology has not been standardized, and the
ranges for adult men are not available at the majority of
hospitals and reference laboratories.
W
hat
are
the main
advancements
in
the
standardization
of
testosterone
levels
?
Recent work with good evidence expressed concern about
the need for standardization of a biochemical test for
diagnosing late-onset hypogonadism. In the opinion of
the authors, the best fraction for diagnosis is FT, but the-
re is a global variation in the literature among authors
with regard to the fraction of testosterone considered va-
lid as a parameter for male hypogonadism diagnosis
21
(
A
).
Efforts to create a standardization of testosterone le-
vels, consensuses about testosterone measurement stan-
dards and reliable reference ranges are being developed
30
(
B
).
According to a study with major evidence, various
types of commercial tests from various non-validated
manufacturers were compared with the gold standard
TT level (LC-MS/MS - liquid chromatography–mass
spectrometry in tandem). The authors concluded that
the majority of manual and automated immunoassays
were capable of distinguishing hypogonadic men from
eugonadic men, if the reference value for adult males
had been established individually at each laboratory, as
there are important variations using the same or diffe-
rent type of test
18
(
A
).
There are various assays available to measure free
and bioavailable testosterone in blood serum. There is
the gold standard dosing method for these values, but as
they take time and are technically complicated, they are
only used by reference laboratories. For example, equili-
brium dialysis is the gold standard for assessment of free
testosterone. Free testosterone can be measured using the
direct method with RIA using a commercial kit, which
is the method used in many laboratories in the country,
with the values obtained being lower than those in the
reference methods
18
(
A
).
The gold standard for measurement of total testoste-
rone is LC-TM/MS, and reliable reference ranges for TT
measurements using this method are being developed
30
(
B
).
Improvements in terms of easiness to read LM-MS/MS
will make more laboratories develop new measurement
procedures. These new levels should be validated for an
international reference developed by a competent referen-
ce laboratory. Standardization is crucial to improve pa-
tient care, otherwise the proliferation of procedures using
the method could impair the LC-MS/MS, which is a me-
thod with good precision. This conclusion is true for all
methods used for the measurement of testosterone
33
(
B
).
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