Chronic yeast infections are commonly attributed to lifestyle issues like using tight underwear, use of over-the counter feminine hygiene products/douches, being overweight or having a diet high in sugar intake, having diabetes, over-use of antibiotics, or having a condition that suppresses the immune system. However, one of the important underlying causes of chronic yeast infection can actually be hormonal imbalance – especially imbalance in sex-hormones like estrogen and progesterone.

Effect of estrogen on infection causing yeast (Candida)

Over the last many years, researchers have consistently found an effect of estrogen on the growth of the yeast, Candida. For example, a study published in 2000 by researchers from Iowa clearly showed that estrogen (specifically, 17-β-estradiol) increased the growth and survival of Candida.

Candida exists in two forms – oval form and filamentous form. A change from the oval to the filamentous form is necessary for infection establishment. Research at the University of Illinois found that 17-β-estradiol, the predominant type of estrogen during reproductive years, supported the conversion of oval form to the filamentous form. On the contrary, 17-β-estradiol, which is similar to 17-β-estradiol but lacks its activity, did not have the same effect. Similarly, neither Estriol (produced in significant amounts during pregnancy), nor Ethynyl estradiol (a derivative of Estradiol commonly used in oral contraceptive pills) had any effect on conversion to filamentous form.

Many women notice an increase in vaginal yeast infections before their periods or around menopause. This is because of the changes in estrogen levels – high before periods and low closer to menopause. Lower estrogen levels cause vaginal dryness which can lead to more injuries to the vaginal tissue and increase the chances of infection.

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Effect of Estrogen on vaginal immunity against infections

A review article published in 2010 describes the role of sex-hormones in immunity of reproductive tract against infections. The vaginal cells have an immune system of their own to prevent infection. However, the reproductive tract also needs to be able to support fertilization and maintain the fetus which, being genetically different, is foreign to the woman’s body. This balance is achieved by the changing levels of sex-hormones with the stage of the menstrual cycle. Thus, lower estrogen levels are protective against infections while an increase in estrogen suppresses the immunity against infections. This immunosuppressive effect of estrogen also seems to be responsible for yeast infections as shown by research published in 2012 by researchers from Arizona.

Effect of progesterone on infection causing yeast (Candida)

An article published in 2014 by scientists from Portugal and UK studied the effect of progesterone on Candida. Progesterone is produced in larger amounts in the luteal phase (between ovulation and start of the period) of menstrual cycle and also during pregnancy. They found that progesterone reduced the infective capacity of Candida. Progesterone achieves this effect by suppressing the genes of Candida needed for establishment of infection.

So what about chronic yeast infections?

You might wonder that if it is natural and normal for a woman to have fluctuating levels of estrogen, shouldn’t the lower levels of estrogen in the non-ovulating phase then take care of the infection? Yes, you are right, it should. Obviously, something else is happening that makes the yeast infection chronic.

A study carried out in mice by an expert from Sharjah, published in 2014, showed that giving estrogen externally to mice predisposed them to severe and persistent vaginal yeast infections.

Several prevalence studies have shown that Candida infections are more common in pregnant women during the second or third trimester of pregnancy. This would correlate directly with the increased levels of estrogen in the second and third trimester. As we have learnt, the higher levels of progesterone during this time should prevent infections. So what is happening in pregnant women who get yeast infection?

Could the cause be hormonal imbalance due to external reasons? The question then changes to what are the external reasons for hormonal imbalance – especially estrogen increase (also called estrogen dominance)?

Endocrine disruptors

A review article by scientists from Kenya and USA, published in 2012, discussed the impact of endocrine disruptors on the immunity against pathogens in the reproductive tract. Endocrine disruptors are molecules in our environment that affect our hormones. These compounds include synthetic chemicals like pesticides, herbicides, plastics, and therapeutic hormones. Some naturally occurring compounds can also act as endocrine disruptors, for example, phytoestrogens – plant derived compounds that behave like estrogens.

Different endocrine disruptors behave differently – some block normal hormonal activity, others mimic the natural hormones, while some others trigger hormone production. Thus, there are external compounds in our environment that can cause estrogen dominance, for example, Bisphenol A (BPA – commonly found in plastic containers used to store foods and beverages) which triggers estrogen activity and phytoestrogens that increase the overall estrogen activity by mimicking estrogen.

So, if there are more of these endocrine disruptors in our environment, there are higher chances of getting hormonal imbalance and the related chronic yeast infections.

1) Does hormone imbalance related chronic yeast infection affect just females or male as well?

Estrogen is a hormone largely produced by ovaries, but also to some extent by adrenal cortex, and testes. So, men also produce estrogen to some extent. Natural hormonal imbalances do occur in men with age. However, estrogen dominance is also increasingly common in men of younger age. Yeast infections are not the commonly described symptoms of estrogen dominance in men. This is understandable due to differences in male and female reproductive anatomy and needs. That being said, there are increased reports of chronic yeast infections in men – these are primarily infections of skin of the genitalia (for example, balanitis). Whether there is a link between estrogen dominance and chronic yeast infection is yet to be determined.

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2) Can hormone replacement cause recurring yeast infections?

Yes. A study published in 2011 by experts from University of Sydney showed clearly that postmenopausal women who took hormone replacement therapy (HRT) were significantly more likely to develop yeast infections. It is possible that this happens because the normal vaginal microbes change in the HRT receiving women, as was described by an earlier study from India. However, it is important to keep in mind that HRT involves external estrogen doses and each body is different and has its own normal limit. Also, it is not naturally normal for a post-menopausal woman to have high amounts of estrogen and therefore even levels of estrogen lower than in pre-menopausal women could be high enough to be considered hormonal imbalance in a postmenopausal woman.

3) What are bioidentical hormones? Are they safer?

Bioidentical hormones are exact duplicates of what your body makes, but is created in a laboratory. They are synthesized by chemical extraction of diosgenin from plants like yams and soy. Diosgenin is then modified chemically to make precursor progesterone which in turn is used to synthesize bioidentical estrogens and androgens. Specialists from Cleveland Clinic have discussed the misconceptions regarding Bioidentical Hormone Therapy (BHRT) in an article published in 2011.

As bioidenticals are an exact copy of the natural hormone, for HRT, they will have the same safety profiles as the natural hormone. FDA does not recognize BHRT and is unaware of any credible scientific evidence regarding its safety, and recommends informed and careful decision while choosing HRT products.