Maturitas
74 (2013) 208–
212
Contents
lists
available
at
SciVerse
ScienceDirect
Maturitas
jo
ur
n
al
hom
ep
age
:
www.elsevier.com/locate/maturitas
Review
The
evidence
for
seasonal
variations
of
testosterone
in
men
Ryan
P.
Smith, Robert
M.
Coward, Jason
R.
Kovac,
Larry
I.
Lipshultz
∗
Scott
Department
of
Urology,
Baylor
College
of
Medicine,
Houston,
TX,
United
States
a
r
t
i
c
l
e
i
n
f
o
Article
history:
Received
27
November
2012
Accepted
6
December
2012
Keywords:
Testosterone
Seasonal
variation
Hypogonadism
Vitamin
D
Melatonin
a
b
s
t
r
a
c
t
Ample
evidence
exists
to
support
the
concept
of
diurnal
variations
in
testosterone
levels;
however,
sub-
stantiation
for
seasonal
fluctuations
is
sparse
and
inconsistent.
Since
circadian
disparities
exist,
laboratory
screening
for
hypogonadism
has
traditionally
been
conducted
using
serum
testosterone
levels
obtained
in
the
early
morning.
Should
circannual
variability
of
testosterone
be
conFrmed,
it
would
make
the
monitoring
of
testosterone
levels
more
difFcult
while
forcing
the
development
of
seasonal
reference
standards
to
allow
for
comparison.
Moreover,
decisions
to
begin
treatment
and
adjustment
of
practice
patterns
would
likely
follow.
This
review
thoroughly
explores
all
of
the
available
evidence
concerning
seasonal
variations
in
testosterone
levels.
The
impacts
of
melatonin,
vitamin
D,
sleep–wake
cycles,
light
exposure,
physical
activity,
BMI,
and
waist
circumference
are
also
discussed.
Current
research
suggests
that
while
some
evidence
exists
to
support
the
notion
of
seasonal
testosterone
variations,
the
discussed
inconsistencies
preclude
the
incorporation
of
this
concept
into
current
clinical
standards.
© 2012 Elsevier Ireland Ltd. All rights reserved.
Contents
1.
Introduction
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208
2.
Seasonal
variations
in
testosterone:
the
evidence
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209
3.
Seasonal
variations
in
testosterone:
influence
of
light
exposure,
melatonin
and
sleep–wake
cycles
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210
4.
Seasonal
variations
in
testosterone:
the
role
of
the
hypothalamic–pituitary–testicular
axis
and
vitamin
D
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210
5.
Seasonal
variations
in
testosterone:
lifestyle
influences?
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210
6.
Conclusions
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211
Contributors
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211
Competing
interests.
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211
±unding
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211
Provenance
and
peer
review
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211
References
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211
1.
Introduction
Testosterone
(T)
contributes
signiFcantly
to
male
development,
reproduction,
and
aging.
Due
to
an
improved
understanding
of
the
links
between
hypogonadism
and
men’s
health,
the
symptoms
surrounding
age-related
declines
in
T
have
become
increasingly
well-recognized.
Indeed,
the
ofFce
evaluation
of
the
aging
male
now
requires
a
thorough
understanding
of
the
relationships
between
male
sexual
function,
hypogonadism,
and
cardiovascular
risk.
The
association
of
hypogonadism
with
metabolic
syndrome,
∗
Corresponding
author
at:
6624
±annin
Street,
Suite
1700,
Houston
77030,
TX,
United
States.
Tel.:
+1
713
798
6163.
E-mail
addresses:
rpsmith@bcm.edu
(R.P.
Smith),
larryl@bcm.edu
(L.I.
Lipshultz).
visceral
adiposity,
erectile
dysfunction,
and
insulin
resistance
requires
the
treating
physician
to
be
astute
concerning
patient
follow-up,
management
and
treatment
related
side
effects
[1]
.
Currently,
testing
for
T
requires
clinicians
to
be
aware
of
the
diurnal
variations
that
exist,
since
improperly
ordered
laboratory
values
can
impact
treatment
decisions.
It
is
well
established
that
diurnal
variations
in
T
levels
exist
with
levels
stable
throughout
the
morning
and
early
afternoon
followed
by
modest
declines
in
the
evenings
[2–4]
.
It
has
been
hypothesized
that
these
variations
are
influenced
by
a
constellation
of
factors
including
melatonin,
age,
sleep–wake
cycles,
and
circadian
rhythms
[5]
.
Given
the
substantial
evidence
for
diurnal
T
variations,
the
Endocrine
Society,
in
its
clinical
practice
guidelines,
recommended
that
adult
men
screened
for
androgen
deFciency
syndromes
have
their
initial
T
levels
drawn
in
the
morning
[6]
.
It
is
tempting
to
speculate
that
similar
variations
could
exist
where
seasonal
0378-5122/$
–
see
front
matter
©
2012 Elsevier Ireland Ltd. All rights reserved.