The 2-OH / 16-OH-E1 Balance is a measure of the ratio between two types of estrogen metabolites in the body: 2-hydroxyestrone (2-OH) and 16-alpha-hydroxyestrone (16-OH-E1).

Estrogen, a hormone primarily produced in the ovaries, plays a crucial role in various bodily functions, including:

(1) regulating the menstrual cycle,

(2) supporting reproductive health,

and (3) maintaining bone density.

However, when estrogen is broken down (metabolized) in the body, it forms different metabolites, some of which may have different effects on health. The 2-OH metabolite is considered to have more favorable properties, potentially exerting protective effects against certain health risks, such as cancer, whereas the 16-OH-E1 metabolite is associated with higher estrogenic activity and may be linked to an increased risk of estrogen-related health issues.

Therefore, assessing the balance between these two metabolites can provide valuable insights into estrogen metabolism and overall health status, helping healthcare providers tailor interventions to promote hormonal balance and reduce health risks.

The 2-OH / 4-OH-E1 Balance refers to the balance between two different forms of estrogen metabolites in the body, specifically 2-hydroxyestrone (2-OH) and 4-hydroxyestrone (4-OH-E1). Estrogen is a hormone that plays a crucial role in various bodily functions, including reproductive health and bone density. When estrogen is metabolized or broken down in the body, it forms different metabolites, and the balance between these metabolites can provide important insights into overall health.

The 2-OH form is often considered less harmful, with potential protective effects against certain health issues, while the 4-OH-E1 form is associated with increased risk for conditions like cancer. Therefore, analyzing the ratio of these two metabolites can help assess estrogen metabolism and provide valuable information for optimizing health and preventing potential risks.

Important Note: If Estrogen metabolite levels are very low, the reproducibility of the test is not as ideal, so calculated ratios (for the methylation-activity index and phase I estrogen metabolism ratios) are more approximate, less certain, and may not be reported.

Research and clinical studies show that the 2-hydroxylated estrogens (2-OH E2 and 2-OH E1) are a safer pathway of hydroxylation than the 4-hydroxyestrogens (4-OH E2 and 4-OH E1), which bind to and damage DNA, leading to mutations that are associated with increased breast cancer risk.

The hydroxylation of estradiol is one of the major routes of metabolism of the estrogen steroid hormone estradiol. It is hydroxylated into the catechol estrogens 2-hydroxyestradiol and 4-hydroxyestradiol and into estriol (16a-hydroxyestradiol). 2-hydroxyestradiol metabolite has several physiological consequences: the ability to influence intracellular signaling, adenohypophyseal hormone secretion, radical and quinone formation and inhibition of tumor formation.

Most consider 2-OH-E1 favorable

Estrogen is metabolized (primarily by the liver) down three phase I pathways. The 2-OH pathway is considered the safest because of the anti-cancer properties of 2-OH metabolites. Conversely, the 4-OH pathway is considered the most genotoxic as its metabolites can create reactive products that damage DNA. The third pathway, 16-OH creates the most estrogenic of the metabolites (although still considerably less estrogenic than estradiol) - 16-OH-E1.

2-hydroxyestrone and 16-hydroxyestrone are Phase I metabolites of Estrone (E1). Their ratio is of clinical significance in pre and peri-menopausal women. In post-menopausal women it does not have the same clinical significance. It is, however, hypothesized that the 2/16 ratio is important in menopausal women who are on hormone replacement therapy (HRT).

There is evidence that methoxylated estrogens, especially the 2-pathway methoxylated estrogens (E1 and E2), are associated with decreased breast cancer risk; 2-MeOE2, produced from 2-OHE2, has been described to have anti-proliferative, antingiogenic, and pro-apoptotic activity in multiple types of cancer.

There is evidence that methoxylated estrogens, especially the 2-pathway methoxylated estrogens (E1 and E2), are associated with decreased breast cancer risk; 2-MeOE2, produced from 2-OHE2, has been described to have anti-proliferative, antingiogenic, and pro-apoptotic activity in multiple types of cancer.

2-OH-3ME-Valeric (aka 3-Methyl-2-oxovaleric acid) is an abnormal metabolite that arises from the incomplete breakdown of branched-chain amino acids. 

Moderate increase may result from lactic acidosis, episodic ketosis, or thiamine/lipoic acid deficiency. Significant elevations are associated with genetic issues, MSUD, and pyruvate dehydrogenase deficiency.

- Slight elevations may be due to deficiencies of the vitamins thiamine or lipoic acid.

- Elevated values are also associated with the genetic diseases maple syrup urine disease or pyruvate dehydrogenase deficiency.

Most consider 2-OH-E1 favorable

Estrogen is metabolized (primarily by the liver) down three phase I pathways. The 2-OH pathway is considered the safest because of the anti-cancer properties of 2-OH metabolites. Conversely, the 4-OH pathway is considered the most genotoxic as its metabolites can create reactive products that damage DNA. The third pathway, 16-OH creates the most estrogenic of the metabolites (although still considerably less estrogenic than estradiol) - 16-OH-E1.

Percentages of 2-OH-E1, 4-OH-E1, and 16-OH-E1

When evaluating phase I metabolism, it can be helpful to compare the percentages of 2, 4, and 16 OH-E1 metabolites. Most individuals metabolize the majority of their estrogens down the 2-OH-E1 pathway which is generally considered the “safer pathway”. This is followed by 16-OH-E1 and 4-OH-E1 respectively, both of which are deemed more reactive and potentially genotoxic.

2-Hydroxyestrone is an endogenous biomarker and major urinary metabolite of estrone and estradiol. Along with 16α-Hydroxyestrone, 2-Hydroxyestrone is used as an indicator for increased risk of cancer.

Most consider 2-OH-E1 favorable

Estrogen is metabolized (primarily by the liver) down three phase I pathways. The 2-OH pathway is considered the safest because of the anti-cancer properties of 2-OH metabolites. Conversely, the 4-OH pathway is considered the most genotoxic as its metabolites can create reactive products that damage DNA. The third pathway, 16-OH creates the most estrogenic of the metabolites (although still considerably less estrogenic than estradiol) - 16-OH-E1.

In a Hormone Metabolite Assessment Panel (HUMAP) for pre-menopausal women, the ratio of 2-Hydroxyestrone (2-OH-E1) to 16-Hydroxyestrone (16-OH-E1) is a critical metric for assessing estrogen metabolism and its implications for health. This ratio reflects the balance between two major pathways of estrogen metabolism: the 2-hydroxylation pathway, leading to 2-OH-E1, and the 16α-hydroxylation pathway, resulting in 16-OH-E1.

2-OH-E1 is generally considered a safer estrogen metabolite due to its weaker estrogenic activity, and it has been associated with a reduced risk of estrogen-related conditions, such as certain breast cancers.

On the other hand, 16-OH-E1 is known for its potent estrogenic effects and has been linked to an increased risk of estrogen-sensitive conditions.