Protein Breakdown

16α-Hydroxyestrone (16α-OH-E1) is a metabolite of estrone, one of the three main estrogens produced by the human body.  It has been associated with various health implications, particularly in hormone-sensitive conditions like breast cancer. 

Laboratory testing for 16α-OH-E1 can provide valuable insights into an individual's estrogenic activity and potential risks related to estrogen dominance. 

Clinically, elevated levels of 16α-OH-E1 are often a concern as they may contribute to the development and progression of certain diseases. 

Fortunately, there are natural ways to modulate these levels, including dietary changes and lifestyle adjustments, which can help in maintaining a healthy hormonal balance and reducing potential risks associated with high levels of 16α-OH-E1.

This article delves into the significance of 16α-OH-E1 as a biomarker, exploring its definition, functions, laboratory testing methods, clinical applications, and implications for healthcare. Additionally, strategies for lowering 16α-OH-E1 levels and optimizing health outcomes are discussed. 

What is 16α-OH-E1?

16α-OH-E1 Definition and Overview

16α-OH-E1, or 16α-hydroxyestrone, is a metabolite of estrogen.  Estrogen is a steroid sex hormone primarily produced in the ovaries in females and smaller amounts in the adrenal glands and adipose tissue in both sexes.  [11.] 

Estrogen is primarily processed by the CYP family of enzymes (although certain other enzymes are involved, often hydroxylases), which convert it to estrone (E1), estradiol (E2), and estriol (E3).  

Estrone (E1) is further processed to 2-hydroxyestrone, 4-hydroxyestrone, or 16α-hydroxyestrone via the same CYP family of enzymes.  Each of these forms of estrone have different health implications.  

16α-OH-E1 is a hydroxylated form of estrone that is converted from estrone via the CYP3A4 enzyme.  It is produced via hydroxylation at the 16th carbon position; this process occurs in various tissues that express the CYP3A4 enzyme, including the liver, adipose tissue, and breast tissue.

16α-OH-E1 Functions and Physiological Roles

Overview of Functions of Estrogens  [8., 18.]

Estrogens play critical roles in various physiological processes including regulating reproductive function and the menstrual cycle, bone health, cardiovascular function, and cognitive function and mood.  

Additionally, estrogen signaling influences lipid metabolism, glucose homeostasis, and immune function.  

It also affects skin elasticity, hair growth, body weight, and fat distribution, while contributing to sexual health by enhancing vaginal wall thickness and lubrication. Additionally, estrogen is crucial for breast development during puberty and preparing for lactation.

Overview of Estrone  [1., 8.]

Estrone (E1) is one of the three main estrogens produced in the human body, alongside estradiol (E2) and estriol (E3). It becomes the predominant form of estrogen in postmenopausal women. 

Estrone is primarily synthesized in adipose tissue through the aromatization of androstenedione, an androgen produced by the adrenal glands and the ovaries. This process becomes especially important after menopause when ovarian estrogen production declines.

Estrogens and Their Interactions with Receptors  [8.]

The actions of estrogens in the body are influenced by the specific structure of each estrogen molecule, the type of estrogen receptor it binds to, and the cellular context. 

Estrogens exert their effects by binding to estrogen receptors, which are part of the nuclear hormone receptor superfamily. These receptors exist mainly in two forms, estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), each encoded by different genes and varying structurally, particularly in their ligand-binding domains. 

This difference in structure affects their affinity for various ligands; for instance, some estrogens and phytoestrogens preferentially bind ERβ, whereas others have a higher affinity for ERα.

Once bound to an estrogen, the receptor undergoes a conformational change, allowing it to dissociate from chaperone proteins and move into the nucleus where it binds to DNA at sites known as estrogen-response elements.  

This binding can either activate or repress the transcription of target genes depending on the presence of coactivators or corepressors in the complex. 

The distribution of estrogen receptors varies across different tissues, which partly explains the tissue-specific effects of estrogen. For example, ERα is predominantly found in reproductive tissues like the endometrium, while ERβ is more common in non-reproductive tissues such as bone and brain. 

This selective expression and the unique interaction of estrogens with their receptors underpin the diverse physiological roles of estrogens, from reproductive functions to their roles in bone density and cardiovascular health.

The Role of 16α-OH Estrone

16α-OH-E1, a metabolite of estrone, exhibits estrogenic activity, although its potency and biological effects may differ from those of other estrogen metabolites such as estradiol.  

Research suggests that it may contribute to estrogen-mediated processes in the body.  

High levels of 16α-OH-E1 have also been associated with certain health conditions, including hormone-dependent cancers such as breast and endometrial cancer, as well as cardiovascular disease and metabolic disorders.  However, it may be protective against osteoporosis.  

Therefore, understanding the regulation and metabolism of 16α-OH-E1 is essential for unraveling its role in health and disease.

16α-OH-E1, Breast Cancer and Estrogen-Positive Cancer Risk  

16α-OH-E1, as a metabolite of estrogen, is important to consider in the context of breast cancer risk, particularly among postmenopausal women.  16α-OH-E1 has been studied for its potential role in cell proliferation comparable to estradiol in estrogen receptor-positive (ER+) breast cancer cell lines. 

Despite having a lower affinity for estrogen receptors than estradiol, research indicates that once bound, it fails to regulate the receptor down, possibly enhancing estrogenic activities more than other metabolites like 2-hydroxyestrone (2-OH estrone).  [6.]

16α-OH-E1 plays distinct roles in the progression of estrogen-receptor-positive (ER+) cancers in general.  16α-OH estrone has pro-inflammatory actions and higher levels may correlate with poor prognosis in ER+ ovarian and uterine corpus carcinomas.  However, more research is needed to better understand the implications of high 16α-OH estrone levels and estrogen-positive cancers.  [5.] 

However, one study involving 340 cases and 677 matched controls of postmenopausal women did not find any significant associations between breast cancer risk and the levels of these metabolites individually or their ratio in the general population of the study.  [6.] 

Notable findings did emerge among specific subgroups. For instance, while no significant associations were observed in women with estrogen receptor-positive/progesterone receptor-positive (ER+/PR+) tumors, a significant positive association was found between both 2-OH estrone and the 2:16α-OH estrone ratio and the occurrence of ER-/PR- tumors.  [6.]

These results suggest that while the overall impact of these metabolites on breast cancer risk may be minimal, their influence could be more pronounced in certain breast cancer subtypes, particularly those that are hormone receptor-negative.  [6.]   

Another paper critiques the use of the 2-OH/16α-OH estrone ratio as a biomarker for breast cancer risk due to deficiencies in assay accuracy and specificity, highlighting the need for improved methods to measure both conjugated and unconjugated forms of these estrogens in serum and urine.  [17.]

These findings indicate the need for further studies to confirm these associations and to better understand the underlying mechanisms.  

It should be noted that elevated 16α-OH estrone levels have been implicated in prostate cancer development; the prostate is a male organ that has estrogen receptors, so may be susceptible to hormones with estrogenic activity.  [4.]

Because of the implications of elevated 16α-OH estrone with certain cancers, assessment of 16α-OH estrone may be warranted in postmenopausal women presenting with vaginal bleeding.  [1.] 

16α-OH Estrone and Cardiovascular Health

Epidemiological studies indicate an increased risk of cardiovascular disease (CVD) in menopausal women, potentially linked to changes in estrogen metabolism.  [9.]

Estrogen metabolites can increase reactive oxygen species (ROS) contributing to DNA damage and oxidative stress, factors associated with neurodegenerative diseases and cancers, though their specific effects on cardiovascular health are less clear.  [9.]

16α-hydroxyestrone (16α-OH-E1) is one estrogen metabolite that may be associated with an increased risk of cardiovascular disease (CVD) in menopausal women.  [9.]  

16α-OH-E1 is known for its potent estrogenic activity at estrogen receptors, which could influence cardiovascular health by affecting vascular and endothelial functions. 

Research involving post-menopausal women from the Genetics of Atherosclerotic Disease (GEA) Mexican Study examined the serum levels of several estrogenic metabolites and their relation to cardiovascular risk and established CVD.  

This study indicated that variations in the levels of certain estrogen metabolites including 16α-OH-E1 were found between women with cardiovascular risk or established cardiovascular disease and healthy controls, suggesting a potential link between higher 16α-OH-E1 levels and increased cardiovascular risk.  [9.]

16α-OH-E1’s estrogenic properties could influence cardiovascular health by affecting vascular and endothelial functions, particularly in menopausal women. However, the precise roles of these metabolites in cardiovascular health remain inadequately understood, necessitating further studies to assess their direct impact on cardiovascular function in this demographic.

Other research points to positive cardiovascular benefits of 16α-OH-E1; in one study, higher levels of 16α-OH-E1 were associated with lower systolic blood pressure (SBP).  [13.]

The formation of 16α-OH-E1 by the enzyme CYP enzyme family may also be influenced by dietary habits, particularly the intake of soluble fibers found in fruits, vegetables, and grains. 

These fibers are thought to enhance the activity of CYP enzyme family, thereby increasing the levels of 16α-OH-E1, which has been shown to exhibit antioxidant properties and promote vasodilation through increased production of prostacyclin and nitric oxide in endothelial cells.  [13.] 

This study posits that the dietary intake of soluble fiber could modulate estrogen metabolism in a way that favorably affects blood pressure regulation.  [13.]  Whether the health benefits noted were due directly to alterations in levels of 16α-OH estrone, or due to the many health benefits of a diet rich in fruits and vegetables, could not be determined from this study alone.  

16α-OH Estrone and Bone Health

16α-OH estrone may be protective for bone health.  Research has shown that postmenopausal women who predominantly metabolize estrogen through the 16α-hydroxylation pathway generally have higher BMD than those who metabolize it through the 2-hydroxyl pathway.  [12.]

This relationship suggests that the active form of estrogen, 16α-OH-E1 supports bone health more effectively than its inactive counterparts, which include 2-hydroxyestrone.

The study also explored the role of genetic and dietary factors in influencing these metabolic pathways. Interestingly, women with a family history of osteoporosis tend to metabolize estrogen more through the inactive 2-hydroxyl pathway, which could predispose them to lower bone density and higher osteoporosis risk. 

Furthermore, calcium dietary intake appeared to influence estrogen metabolism, with higher calcium intake correlating with increased levels of both active and inactive estrogen metabolites.

Overall, the findings suggest that the metabolic pathway of estrogen in postmenopausal women can significantly impact their bone health, influenced by genetic background and dietary habits. This indicates potential areas for preventive strategies in women at risk of osteoporosis, possibly through dietary modifications or interventions aimed at altering estrogen metabolism.

Laboratory Testing for 16α-OH-E1

Overview of Testing, Sample Collection and Preparation

Urine samples are commonly used for 16α-OH-E1 testing.  

Estrogen metabolites can be excreted in the urine, making it a reliable method for testing estrogen detoxification and comparing ratios of estrogen metabolites.  Urine testing specifically assesses phase I estrogen detoxification, and it can also be used to assess phase II methylation detoxification.    

Urine collection can be easier and less stressful for patients compared to blood draws, as samples can be collected at home without the need for a clinical setting.  Additionally, urinary levels can reflect longer-term hormone exposure rather than the transient levels often seen in blood, as it reflects detoxification patterns (rather than providing snapshots of levels in the bloodstream).

Interpretation of 16α-OH Estrone Test Results

Reference Range for 16α-OH Estrone

It is important to consult with the lab company providing testing for 16α-OH estrone levels.  For reference, one lab provides the following reference range for serum 16α-OH estrone levels:  [14.]

For cycling women in the luteal phase: 0.7-2.6 ng/mg

For postmenopausal women not supplementing with hormones: 0.2-0.6 ng/mg

Optimal Levels of 16α-OH-E1

Hormones never act alone, and their effects are nuanced.  Optimal levels of 16α-hydroxyestrone (16α-OH estrone) in urine tests vary depending on individual health conditions, gender, and age, but generally, maintaining a lower level is considered healthier due to its strong estrogenic activity and potential links to increased cancer risk.

Health professionals often recommend that women remain within the reference range of 0.7-2.6 ng/mg in urine samples, although their recommendation will be affected by many factors including the patient’s overall health, detoxification capacity, personal and family health history, time of life, diet and lifestyle, medications, and other factors.  

Regular monitoring through urinary tests is essential to ensure that the metabolite levels are within a safe range, thereby reducing the potential for DNA damage and promoting better hormonal balance and overall health.

Clinical Significance of High 16α-OH-E1 Levels

Because 16α-OH-E1 has estrogenic activity at estrogen receptors, elevated levels may indicate an unwanted overstimulation of estrogen-sensitive tissue at the breasts, endometrium, and prostate.

Premenopausal women, or women supplementing with estrogen who complain of estrogen excess symptoms, should be assessed for estrogen and estrogen metabolite levels.  

See below for more information on natural methods to lower 16α-OH-E1.  

Clinical Significance of Low 16α-OH-E1 Levels

Typically, declining levels of estrogen and its metabolites are seen postmenopausally.  Testing of estrogen metabolites may be recommended for women complaining of menopausal symptoms.  

Additionally, postmenopausal women with a family or personal history of osteoporosis or low bone mineral density should consider testing their estrogen and estrogen metabolite levels. 

16α-OH-E1 Related Biomarkers to Test

Several other biomarkers are associated with estrogen metabolism and activity.  Other estrogen metabolites including 2-hydroxyestrone (2-OH-E1) and 4-hydroxyestrone (4-OH-E1), as well as estrone (E1), estradiol (E2), and estriol (E3) levels should be considered.  

2-Hydroxyestrone (2-OH estrone)

2-OH estrone is considered a "good" estrogen metabolite because of its weak estrogenic effects, which are thought to be protective against breast cancer.  2-OH estrone binds to estrogen receptors but does not stimulate them as strongly as other forms of estrogen or its metabolites, calming the overall estrogenic effect.

Testing for 2-OH estrone provides a balance perspective by contrasting its levels with those of stronger estrogens like 16α-OH estrone, potentially offering insights into cancer risk and hormonal balance.

4-Hydroxyestrone (4-OH estrone)

4-OH estrone is another metabolite of estrone with strong estrogenic properties and potential carcinogenic effects. 

Specifically, 4-OH estrone is known for its potential to form quinones that can directly damage DNA and generate reactive oxygen species, increasing the risk of mutagenesis.

Measuring 4-OH estrone alongside 16α-OH estrone and 2-OH estrone can help assess the overall estrogenic and carcinogenic potential within the body.

Estrone (E1)

Estrone is a weaker estrogen compared to estradiol but is prevalent in postmenopausal women and can be converted back to estradiol. 

Testing for estrone is important for understanding the overall estrogenic activity, especially in postmenopausal women who are at increased risk for estrogen-sensitive cancers.

Estradiol (E2)

Estradiol is the most potent estrogen and has significant implications for bone density, reproductive health, and cardiovascular health.  Monitoring estradiol levels is essential for assessing reproductive health and menopausal status, and for managing hormone replacement therapy effectively.

Estriol (E3)

Estriol is a weak estrogen predominantly produced during pregnancy. Outside of pregnancy, its levels are very low, but it has been suggested to have protective effects against breast cancer. 

Testing for estriol, especially in non-pregnant states, might provide additional insights into estrogenic activity and potential protective mechanisms against estrogen-related pathologies.

How to Lower 16α-OH-E1?  Natural Ways to Lower 16α-OH-E1

It is always essential to work with a qualified healthcare professional in any case of hormone imbalance.  The following diet and lifestyle measures have been shown to naturally promote healthy hormone balance:

Dietary Fiber Increase: consuming more fiber helps bind estrogen in the digestive tract, promoting its excretion and reducing reabsorption.  [7.]  

Interestingly, one study of 240 women also showed a correlation between increased fiber intake and anovulation, possibly due to lower estrogen levels.  [7.]

Cruciferous Vegetables: foods like broccoli, cauliflower, and Brussels sprouts contain indole-3-carbinol, which aids in detoxifying excessive estrogen and optimizing hormone balance.  [3.] 

Regular Exercise: physical activity can help balance hormones by improving metabolism and reducing fat, which is significant since body fat can produce and store estrogen.  [16.]

Probiotics and Gut Health: a healthy gut flora supports proper digestion and detoxification processes, including the breakdown, elimination and balance of hormones like estrogen.  [10.]

Limit Alcohol and Caffeine: reducing intake of substances that can impair liver function helps ensure the liver effectively processes and removes excess hormones.  [15.]

‍Stress Management: stress may have an impact on estrogen levels and metabolism; techniques such as yoga, meditation, or even simple breathing exercises can reduce cortisol levels and help maintain a healthy hormonal balance.  [2.]

Testing 16α-OH-E1 Levels

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