Oestrogen modulation

Oestrogen-like compounds and oestrogen receptor activity

Many compounds—both natural and synthetic—may mimic endogenous sex hormones.^4,22,23 Several chemicals in current industrial use may interfere with the body’s hormone responses. Compounds such as dioxins, polychlorinated biphenyls (PCBs) and bisphenols (found in pesticides, petrochemicals and plastics) may bind to and activate endogenous oestrogen receptor sites. However, unlike natural hormones these xenoestrogens (literally ‘foreign oestrogens’) may exert effects many times more potent than endogenous oestrogens.²⁴ Phytoestrogens (literally ‘plant oestrogens’) also bind to and activate these oestrogen receptor sites although they are often much less powerful than regular oestrogen and therefore act as oestrogen modulators by preventing the more powerful compounds—endogenous hormones and the xenoestrogens—binding in excess oestrogen conditions but binding to empty sites in oestrogen-deficient conditions.²⁵ A compound exhibiting this activity is known as a selective oestrogen receptor modulator (SORM)—similar in effect to the pharmaceutical compound tamoxifen. The isoflavones (such as genistein and dadzein) from soy products, lignans from lentils and flaxseed, coumestans from Trifolium pratense and flavonoids found in a variety of sources are examples of phytoestrogens. Sources of phytoestrogens are listed in the box below. Although most research has focused on phytoestrogenic compounds from soy products, most dietary consumption of these compounds in Western diets occurs from lignans.²⁶ Different soy products may also vary in their phytoestrogenic content: soybeans, tofu and tempeh are good sources while soy milk is generally not. Studies suggest that Cimicifuga racemosa may contain negligible amounts of phytoestrogenic compounds while still exerting strong oestrogen modulating ability.¹³ This is thought to be related more to its effects on luteinising hormone. V. agnus-castus has also shown significant competitive binding to oestrogen receptors in vitro.²⁷

Table 19.1 Relative phytoestrogenic content (μg/100 g) of commonly used therapeutic supplements^{2,14,15,33,34}

The generalisation that all phytoestrogens are inherently weaker than endogenous oestrogen is not correct. The herbs T. pratense and Humulus lupulus actually exert stronger activity in the body than endogenous oestrogen. This may make them therapeutically useful in oestrogen-deficient conditions—those associated with menopause, for example—but may potentially exacerbate symptoms of oestrogen-dependent disorders and render their use inappropriate in high doses in conditions such as endometriosis.^28,29 It is also prudent to avoid herbs known to promote oestrogenic symptoms, such as Chamaelirium luteum and Dioscorea villosa. Studies suggest that long-term treatment with high-dose phytoestrogenic compounds (in excess of 150 mg of soy isoflavones daily for 5 years) can lead to endometrial hyperplasia.³⁰ This suggests a role for lower doses associated with modified dietary intake for long-term management. Cruciferous indoles, in addition to their activity on oestrogen excretion and conversion, may also directly inhibit stimulation of oestrogen receptors by oestrogen or oestrogen-like compounds^31,32 though the particular mechanism is unknown at this time.

Oestrogen excretion

Inadequate oestrogen excretion may result in excess circulating oestrogens. The main route of elimination of excess oestrogens is the liver. The major pathways of elimination are the phase II liver pathways glucoronidation, sulphation and methylation.³⁵ These pathways bind the used hormones with a water-soluble substance, which can then be eliminated through bile and eventually faeces.

If toxins overload the system, these pathways can become congested. Cruciferous indoles, such as indole-3-carbinol (I3C) and di-indolyl-methane (DIM), found in brussels sprouts, broccoli, cabbage, garlic and other ‘sulfurous’ vegetables,³⁶ are

particularly useful for the oestrogen-specific pathways as they induce enzyme reactions that assist with detoxification and conversion of 17β-estradiol to less active forms (2-hydroxyestrone as opposed to 16α-hydroxyestrone).^37–43 While these trials are largely based on direct supplementation (of 300–400 mg/day of I3C or 100 mg/day of DIM) studies suggest food supplementation may also be effective.^36,39,44 Herbs such as Silybum marianum and Bupleurum falcatum can also improve liver enzyme activity in regards to oestrogen clearance.⁴⁵ Figure 19.2 shows examples of supplements, foods and herbs useful in improving liver function. Rosmarinus officinalis has been found to directly increase hepatic metabolism of oestrogens and reduce their uterotropic action in animal studies.⁴⁶ Vitamin B complexes may increase the inactivation of oestrone in the body.⁴⁷ Other useful treatment tools are listed in Table 19.2.

Figure 19.2 Factors affecting oestrogen conversion pathways

Table 19.2 Detoxification enzyme reactions involving common naturopathic medicines

∗ For simplification purposes, phases I and II have not been split into their components.

Phase I liver detoxification processes convert oestrogens to either 2-hydroxyoestrone (2OH oestrone), 16- or 4-hydroxyoestrone. 2OH oestrone is a ‘cancer-protective’ metabolite (oestrogen antagonist) and the latter two are ‘pro-carcinogenic’ (oestrogen agonists).⁴⁸ Each of the enzymes involved are subject to genetic polymorphisms that are measurable in more complex cases. Other factors can also affect this oestrogen conversion (see Figure 19.3).⁴⁸

Figure 19.3 Biochemical and nutritional factors affecting oestrogen conversion and metabolism

The liver is not the only organ associated with oestrogen excretion. The entero-hepatic circulatory system will recycle sex hormones if intestinal transit time is sufficiently slow. If there is not enough fibre in the diet, the oestrogens will be recirculated before they are excreted. Increased fibre consumption has been associated with lower oestrogen metabolites.³⁴ Fibre is also required to increase dioxin, PCB and other oestrogen-like molecules from the body in animal models.^49,50

Supporting liver function

Healthy detoxification consists of both appropriate phase I and phase II detoxification. Phase I is a stage in which lipid soluble substances are transformed into intermediate substances via the cytochrome P450 set of enzymes.³³ In many instances this may render substances even more toxic or otherwise reactive than previously.³³ Therefore appropriate phase II detoxification processes need to be supported. Phase II processes make the intermediate substances from phase I detoxification water-soluble by conjugating them with amino acids like glucoronic acid, glutathione and glycine or undergoing processes such as methylation, sulphation, acetylation and sulphoxidation.³³ These substances can then be excreted through the stool, sweat or urine (and to lesser extent lungs)—elimination pathways, which also need to be appropriately encouraged in detoxification.

Phase I (p450) enzymes are relatively resistant to depletion due to nutritional considerations; however, Phase II enzymes are particularly dependent on nutritional substrates required for conjugation. Pathological factors, such as cardiovascular, liver and kidney disease, can also affect the liver’s detoxification mechanisms. Like many medications, naturopathic medicines have the ability to interact with detoxification pathways in the liver.

Many studies are either in vitro or animal in vivo and therefore clinical significance often remains unknown. It should also be noted that there often exists a lack of in vivo–in vitro correlation with respect to studies on interaction of phase I interactions. For example, while Silybum marianum has documented in vitro evidence of induction of cytochrome p450 enzymes, in vivo evidence does not seem to suggest a significant effect.^81–83 Further studies have also demonstrated that co-administration of S. marianum with other medications does not reduce levels of that medication, again suggesting no clinically significant interaction.^84–87 The induction of CYP enzymes by H. perforatum also seems to bear little clinical significance when compared to in vitro results.^88,89 However, quality issues need to be considered as evidence suggests that specific compounds in naturopathic medicines that vary from product to product may be responsible for this induction—for example, levels of hyperforin may be responsible for induction in H. perforatum products and these levels can differ significantly in different products.^88,90 However, a number of factors can belie in vitro pharmacokinetic suggestion in human physiology, including not just individual differences in people themselves, but also significant differences in different versions of the ‘same’ naturopathic products. Therefore caution should still be observed. It should also be noted that in a clinical setting induction or inhibition of phase I or phase II enzymes, and by extension possible interaction with other medications, does not necessarily preclude use of these naturopathic medicines. Rather it implies that these factors should be taken into appropriate consideration when prescribing them and that the patient’s use of concomitant medicines should be routinely monitored (see the drug–CAM interactions table in Appendix 1).

In some instances dietary inclusion may be more beneficial than supplementation. Glutathione—a key nutrient in phase II metabolism of toxins—is best obtained from food sources, as many supplements may have limited bioavailability.³⁶ Diets low in protein may predispose patients to lowered liver detoxification, as key amino acids are involved in these liver processes.⁹¹ Increasing crude protein intake will also help to improve availability of amino acid precursors to conjugation.

Detoxification

Inhibiting phase I reactions is generally thought of as cancer protective, as it reduces the production of potentially toxic intermediates. However, supporting phase II reactions will also reduce exposure to these intermediates. Antioxidants are also an essential part of detoxification protocol. The liver-supportive naturopathic medicines glutathione and Silybum marianum work largely through their antioxidant activity, sequestering these potentially dangerous or mutagenic intermediate compounds.

Improving liver function, with respect to supporting and implementing balance between phase I and phase II reactions, remains the primary treatment aim in supporting detoxification. However, this process can be supported in other ways.

Modulation of intestinal microflora with probiotics and synbiotics (including dietary intervention with yoghurt) has also been demonstrated to improve the liver’s general function and detoxification ability in humans, most probably through the reduction of endotoxin load or ammonia production and resorption in the intestine.^92–95

Exercise will also promote hepatic biotransformation processes.^96,97 Fasting is also known to enhance the detoxification process,⁹⁸ in part because the main source of energy is hydrolysed fatty acid tissue from adipose tissue stores, where many toxins are stored.⁹⁹