2-Methylhippuric Acid (2MHA) is a substance your body makes when it breaks down xylene, a chemical solvent commonly found in paints, glues, cleaning products, pesticides, perfumes, and fuels. Testing urine for 2MHA is a simple way to check for recent xylene exposure.

A “Moderate” result for 2-Methylhippuric Acid (2MHA) in urine suggests xylene exposure above baseline but not in the high or critical range. This usually reflects recent or ongoing contact with products containing xylene—such as paints, solvents, fuel, or industrial fumes—rather than severe or acute poisoning.

What Does "Moderate" Mean?

• Levels are above the optimal or expected range but below those linked with high risk or acute toxicity.

• May indicate regular or occupational exposure rather than accidental overexposure.

• Shows that the body is actively processing and excreting xylene.

What Should Patients Do?

• Review possible exposure sources at work, home, or in your environment.

• Take steps to minimize unnecessary contact, such as improving ventilation, using protective gear, or switching to safer products.

• If you experience symptoms (headaches, dizziness, fatigue, brain fog), discuss results with your healthcare provider for evaluation and possible repeat testing.

Key Takeaway

A “Moderate” 2MHA result is a signal to pay attention, but not a cause for alarm. It highlights that your body has processed some xylene and that reducing exposure can support long-term neurological, immune, and overall health.

Methylsuccinic acid is a normal metabolite found in human fluids. Increased urinary levels of methylsuccinic acid (together with ethylmalonic acid) are the main biochemical measurable features in ethylmalonic encephalopathy, a rare metabolic disorder with an autosomal recessive mode of inheritance that is clinically characterized by neuromotor delay, hyperlactic acidemia, recurrent petechiae, orthostatic acrocyanosis, and chronic diarrhea. The underlying biochemical defect involves isoleucine catabolism. 

Moreover, methylsuccinic acid is found to be associated with ethylmalonic encephalopathy, isovaleric acidemia, and medium-chain acyl-CoA dehydrogenase deficiency, which are also inborn errors of metabolism.

Note: These tests are used to check for rare metabolic disorders, usually in infants. There is no apparent reason nor benefit to checking ethylmalonic and methylsuccinic acid levels in adults who aren’t suspected to have rare genetic disorders.

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).

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).

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 / 16-OH-E1 Balance is an important marker that helps assess how your body processes estrogen, which is a hormone present in both men and women. While estrogen is often associated with female health, men also produce and rely on it for various bodily functions, including maintaining bone density, cardiovascular health, and proper brain function.

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.

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.

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.

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-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.

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.

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-OH-E1 % (Pre-menopausal) shows what share of estrone is routed down the 2-hydroxylation pathway to 2-hydroxyestrone—a distribution metric, not a disease diagnosis. A lower percentage suggests a relative shift toward 4-/16-hydroxylation, while a higher percentage indicates more 2-OH routing, which is generally fine if 2-methoxy metabolites are adequate (reflecting healthy COMT/methylation). Your result can be influenced by diet (crucifers, I3C/DIM), alcohol, medications/smoking, cycle timing, and collection quality. Interpret against your lab’s reference range, aim for balanced pathways (not “max 2-OH”), and consider food-first methylation support, fiber, sleep, stress management, and clinician guidance if patterns are off.