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Low Sex Hormone Binding Globulin (SHBG) in PCOS and How to Increase it Naturally

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A common feature of PCOS is the finding of low sex hormone binding globulin or SHBG on blood test results.

What does SHBG do?

The purpose of SHBG is to bind to oestrodiol (a type of oestrogen) and testosterone (particularly dihydrotestosterone or DHT they type of testosterone that binds to receptors in hair follicles causing excess hair and hair loss).  When SHBG is bound to these hormones, it inhibits their function, preventing them from floating around the bloodstream freely and being available to act on cell receptors.  Essentially SHBG manages the bioavailability of the two main sex hormones, testosterone and oestrogen.  Low levels of SHBG result in increased activity of these hormones which can show up as excess body hair, head hair loss and acne.  Progesterone, cortisol and other corticosteroids are bound in the same way to a substance called transcortin.  High levels of transcortin can also decrease SHBG.

Where does it come from?

SHBG is produced predominantly by the liver, though the uterus and brain also produce a little as well as the placenta in pregnant women, so a good place to start is a liver supporting herb such as St Mary’s Thistle or Burdock and castor oil heat packs to increase and support liver function.  The liver is also responsible for filtering out and breaking down excess hormones, such as are present in PCOS, so the benefits from this are many.

Firstly, why is it often low in PCOS?

High levels of insulin and insulin-like growth factor 1 (IGF-1) and androgens like testosterone and DHEAS are known to decrease the amount of SHBG produced.  Controlling insulin and blood glucose levels is therefore of paramount importance, both for PCOS in general and specifically in relation to SHBG levels as all of these things are closely related.

Which hormones increase SHBG?

Oestrogen, thyroxine (a thyroid hormone) and human growth hormone increase the production of SHBG, however, attempting to increase any of these is not an appropriate approach, unless they have been formally identified as being low in the relevant blood tests.  In any case, women with PCOS are more likely to be oestrogen dominant.

What can you do to increase SHBG?

Reduce sugar consumption

A study in mice published in 2007 found that eating too much sugar in the form of monosaccharides like glucose and fructose lowered SHBG levels by down-regulating a protein called hepatocyte nuclear factor-4a which controls the function of several genes.  Reducing sugar consumption is a cornerstone in the successful treatment of PCOS, in any case. 

Include soy in your diet

A small study in Chile found that dietary isoflavones such as soy improved SHBG levels by at least 30% in post-menopausal women in just 10 weeks of drinking a small amount of soy milk each day.  The women took 30 grams of a powdered soy milk divided into three servings throughout the day, estimated to provide 69mg of the isoflavones diadzein and genistein.  Phytoestrogens such as those contained in soy may be worth considering if an increase in SHBG is desired, however it should be noted that diadzein and genistein have been found to inhibit thyroid function, which may already be impaired in women with PCOS.

Include green tea and possibly coffee

A slightly larger study in Japan found a positive effect between a high intake of green tea, coffee and total caffeine intake and increased SHBG levels in premenopausal women.  Green tea, but not caffeinated coffee was additionally found to be correlated with lower oestradiol levels in the follicular phase of the menstrual cycles of the subjects which may account for protective effect against breast cancer which has been noted in relation to green tea.  Whilst caffeine has many negative health effects, including in relation to insulin sensitivity, regular consumption of green tea has been consistently found to be associated with positive effects, including a strong antioxidant effect and improvements in insulin sensitivity.

More Information:

Pino AM, Valladares LE, Palma MA, Mancilla AM, Yanez M, Albala C. Dietary isoflavones affect sex hormone-binding globulin levels in postmenopausal women.  J Clin Endocrinol Metab. 2000 Aug;85(8):2797-800.

Nagata C, Kabuto M, Shimizu H.  Association of coffee, green tea, and caffeine intakes with serum concentrations of estradiol and sex hormone-binding globulin in premenopausal Japanese women.  Nutr Cancer. 1998;30(1):21-4.

Selva DM, Hogeveen KN, Innis SM, Hammond GL.  Monosaccharide-induced lipogenesis regulates the human hepatic sex hormone–binding globulin gene.  J Clin Invest. 2007; 117(12):3979–3987 doi:10.1172/JCI32249

“Too much sugar turns off gene that controls the effects of sex steroids”. 2007-11-07.
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