Many men have learned that SHBG binds to a little over half of their
testosterone molecules and renders them "inactive". Because of this, as
SHBG goes up, unbound testosterone goes down. Many physicians like to
focus on free testosterone, which is your T that is not bound to SHBG or another
protein called albumin. And the rule is simple: as SHBG goes down,
free testosterone goes up. And free testosterone is considered the form of
testosterone that is active and available to act on tissues.
NOTE: It is actually a little more complicated than that as testosterone
bound to albumin can be easily unbound and used as well. But the point
remains the same.
So clearly a man wants low SHBG, since it indicates that his free testosterone
would be improved, right?
Wrong! As it turns out, low SHBG is often a sign of many of the worst
chronic diseases that we face in modern, civlized societies.
1. Obesity and Being Overweight. Low SHBG is associated with
obesity.  The reason is probably due to a loss of insulin sensitivity as
we'll discuss below.
2. Lower Insulin Levels. There is evidence that increasing insulin
lowers SHBG.  Studies have found this both in vitor and in vivo as
well, i.e. on human subjects and male ones at that.  Therefore, SHBG is often
a flag or warning signal of insulin and blood sugar issues. In other words, SHBG
does not cause insulin resistance but does indicate it.
NOTE: You may also want to read my link on
The Causes of High SHBG.
3. Cardiovascular Disease, Diabetes, Metabolic Syndrome and Decreased
Longevity. Due to #1 and #2, mumerous studies have shown that low SHBG can
actually indicate decreased longevity. For example, one study found:
"Low SHBG and IGFBP-1 were both associated with an increased prevalence of
abnormal glucose tolerance and the metabolic syndrome, but only SHBG was
associated with diabetes mellitus. SHBG was less influenced by body mass index
than IGFBP-1. Low SHBG indicated increased cardiovascular and coronary disease
mortality; the association remained after adjustment for abnormal glucose
tolerance, but not after adjustment for prevalent cardiovascular disease." 
This is about as ugly as it gets. Low SHBG is correlated with three of the
biggest killers of men: heart disease, diabetes and Metabolic
Syndrome. A more recent and larger scale study verified the above results
but did find that all mortality risk was due to its association with diabetes,
lowered HDL and weight gain. So SHBG does not seem causative, but rather often a
sign that something else is wrong. By the way, it was "ischemic heart
disease" risk that was associated with lowered SHBG in this case, which
basically means accelerated arteriosclerosis and decreased blood supply to the
I document in my link on Apnea and Testosterone how apnea
can affect your baseline testosterone levels by 30 percent or more. Other studies have
shown that SHBG significantly lowers SHBG as well.  So if you have low testosterone and low SHBG,
this is something to consider.
5. Obesity. Because weight gain can lead to loss of insulin sensitivity,
low SHBG values are correlated to extra weight.
6. Inflammation. One study (in women) found that lowered SHBG was
associated with elevated CRP (C-Reactive Protein), one of the "gold standard"
markers of systemic inflammation that is linked to heart disease, dementia and
autoimmune disorders. 
7. Hypothyroidism. One study found that low SHBG was associated with
hypothyroidism and could even be reversed by correcting the underlying thyroid
8. Elevated Triglycerides. Several studies have found that elevated
triglycerides, which are a risk factor for both heart disease and erectile
dysfunction, are also tied in with low SHBG.  Of course, this should be no
shock since elevated triglycerides usually come from eating meals with an overly
high glycemic load and refined carbohydrates.
NOTE: HRT will lower SHBG some and steroid usage even moreso.
Low SHBG Solutions
So, as you can see, having low SHBG and the supposedly
elevated free testosterone that accompanies it, is usually nothing to brag about.
means that, in general, if you have low SHBG, you should find the underlying cause and correct it.
This may not be as easy to do as you might think, because most doctors are very
unlikely to do anything about a lowish value of SHBG, because the lab ranges are VERY wide.
On the Peak Testosterone Forum I have seen
ranges such as 7-47 nmol/l, 10-50 nmol/l or even 10-80 nmol/l. In all cases the
lower value for SHBG is extremely low and so will not even be on your doctor's
However, values below about 20 can be indications of underlying issues and
should not be ignored in my opinion.
Hopefully, one way or another you can get your doctor to consider doing the
1. Monitor. Test you for any of the
(appropriate) conditions above. Many of
these you can get as part of a standard physical or well-being check, so you may
want to ask your physicain about that possibility.
2. Correct Medical Conditions. Correct any issues found in #1. Work with your doctor and do what
you have to do: treat your thyroid dysfunction; exercise; lower the
glycemic load of your diet; lose those extra pounds; get a CPAP machine.
There are also many natural ways to raise SHBG as well. Of course, it is
most important to correct underlying medical conditions, but here are some other
methods that can help:
3. Coffee. Several studies on women showed that coffee raised SHBG.
Finally, this was verified in a study on men as well. 
4. Green Tea. A couple of studies, admittedly on women, have shown that green tea
increases SHBG levels. 
5. Lower Fat Diets and Fiber. One study on men showed that low fat diets
probably due to the fact that they increase insulin sensitivity.  So one simply way to likely raise your SHBG a little
is to eat a low glycemic, low fat diet. I discuss in my link on
Low Fat Diets and Diabetes
that this way of eating will likely reverse any prediabetes
or diabetes that you have and lower arterial plaque at the same time. A
smiliar study echoed the same result and suggested that fiber may play a role as
well.  See also my link on Fat and Fiber for more
6. T3 and T4 (If Hypothyroid). One study found that "Thyroid hormones (triiodothyronine (T3) and thyroxine (T4)) increase
SHBG accumulation in HepG2 cell culture
medium over 5 days, and increase cellular SHBG mRNA levels."  A hypothyroid man that goes on thyroid medication will often
see his low SHBG rise.
NOTE: For more information, see my link on the Causes of High SHBG and
What about HRT and Low SHBG?
The concerns here are that 1) adding HRT may lower an already low SHBG even
further, 2) may sidetrack a man from dealing with underlying medical issues and
3) will simply create an overabundance of free estradiol.
Now I definitely agree with 2. All reasonable underlying issues should be
tracked and investigatedby by or with your doctor. Argument 1, however, may be weak.
To test this hypothesis, it would be best to look for research with participants
likely to have low SHBG. One such study was done on senior men with Metabolic
Syndrome (prediabetes) and the researchers found that giving these men
testosterone gel did indeed lower their SHBG a little. However, this was
for a very small net change in testosterone. 
The same study boosted men's testosteorne much more significantly with
testosterone undecanoate and actually found that the particpants' SHBG rose.
Thus in this case, the testosterone actually helped. Why did the
undecanoate do the trick where the gel did not? The reason is probably the fact that the undecanoate gave over a 100% increase in testosterone and
testeosterone lowers insulin.
As far as #3, one has to realize that the difference in, say, free testosterone
from low to midrange SHBG is not that great. For example, let's say you
were a lowish testosteorne guy with total testosterone of 400 ng/dl and had SHBG
of 32, which is a very "normal amount". That SHBG of 32 nmol/l would give
you a free testosterone level of 8.31 ng/dl. A man with SHBG of 20 and
total T of 400 would have free testosterone of 10.5.
This is an increase of 26% in free T. Now this is a bump, admittedly, but it is
not the kind of bump that is going to make that much difference. Thus SHBG does
matter, but it is not the force of nature that many men think it is when it
comes to elavating testosterone levels. However, it does matter in the
sense that it can foreshadown many medical conditions that need to be dealt
However, what I hear "on the streets" is that men who are low SHBG or just high
converters to estrogen tend to do better with 3X weekly subQ injections. I
believe the reason for this is that with smaller doses of testosterone cypionate
more often, you get a smoother ride with lower estradiol peaks. The reason
this is probably important is that if you are low SHBG, then you are going to be
higher free estradiol. And, of course, elevated free estradiol causes many
issues for us men.
The Journal of Clinical Endocrinology & Metabolism, Mar 1 2005, 90(3):1550-1556,
"Sex Hormone-Binding Globulin and Insulin-Like Growth Factor-Binding Protein-1
as Indicators of Metabolic Syndrome, Cardiovascular Risk, and Mortality in
2) The Journal of Steroid Biochemistry and Molecular Biology, Jun 1995, 53(1-6):
"Interrelations between sex hormone-binding globulin (SHBG), plasma lipoproteins
and cardiovascular risk"
3) The Journal of Clinical Endocrinology & Metabolism, Jul 1 1996,
81(7):2515-2519, "Acute and chronic regulation of serum sex hormone-binding
globulin levels by plasma insulin concentrations in male noninsulin-dependent
diabetes mellitus patients"
4) Diabetes Care, May 2004, 27(5):1036-1041, "Testosterone and Sex
Hormone–Binding Globulin Predict the Metabolic Syndrome and Diabetes in
5) Arch Intern Med. 2007; 167(12):1252-1260, "Sex Steroids
and All-Cause and Cause-Specific Mortality in Men"
6) International Journal of Impotence Research, 2003, 15(Suppl 4):S14–S20,
"Hypogonadism and diabetes"
7) J Clin Endocrinol Metab, 1989 Feb, 68(2):352-8, "Neuroendocrine dysfunction in
sleep apnea: reversal by continuous positive airways pressure therapy"
8) Ann Epidemiol, 2006 Feb, 16(2):105-12, Epub 2005 Oct 10, "Sex hormone-binding
globulin and serum testosterone are inversely associated with C-reactive protein
levels in postmenopausal women at high risk for cardiovascular disease"
9) Horm Res, 1990,34:215–218, "Reproductive Endocrine Functions in Men with
Primary Hypothyroidism: Effect of Thyroxine Replacement"
10) Am J Clin Nutr, l996, 63:22-3l, "Association of dietary factors and selected
plasma variables with sex hormone-binding globulin in rural Chinese women"
11) Journal of Andrology, 29(1):102–105, January-February 2008"A Dose-Response
Study of Testosterone on Sexual Dysfunction and Features of the Metabolic
Syndrome Using Testosterone Gel and Parenteral Testosterone Undecanoate"
12) Eur J Endocrinol, Aug 1 2003, 149:145-152, "The associations of age,
lifestyle factors and chronic disease with testosterone in men: the Tromso
13) Reproductive Sciences, Jan 2006, 13(1):63-68, "Effects of Chinese Green Tea on Weight, and Hormonal and Biochemical Profiles
in Obese Patients With Polycystic Ovary Syndrome—A Randomized Placebo-Controlled Trial"
14) The Journal of Clinical Endocrinology & Metabolism, May 1 1987,
64(5):1083-1085, "DIETARY LIPIDS : AN ADDITIONAL REGULATOR OF PLASMA LEVELS OF
SEX HORMONE BINDING GLOBULIN"
15) Am J Clin Nutr, Dec 1996 64(6):850-855, "Effects of dietary fat and fiber on
plasma and urine androgens and estrogens in men: a controlled feeding study"
16) Journal of Molecular Endocrinology, 2009, 43, 19–27, "Thyroid hormones act
indirectly to increase sex hormone-binding globulin production by liver via
hepatocyte nuclear factor-4a"