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How SHBG and the rs6259 Variant Affect Testosterone and Your Health

Sex hormone binding globulin or SHBG is a protein made by the liver that binds testosterone and other sex hormones in the blood. The amount of SHBG determines how much testosterone is bound and how much is free and active. The rs6259 variant in the SHBG gene influences SHBG levels. Different genotypes at rs6259 are linked to higher or typical SHBG, which can change free testosterone availability and influence energy, mood, libido, body composition, and metabolic health.

Why free testosterone matters

Total testosterone measures all testosterone in the blood. Free testosterone is the small portion that is not bound to SHBG and can enter tissues to exert effects. Two people with the same total testosterone can have different free testosterone if SHBG levels differ. Symptoms such as low energy, reduced libido, decreased muscle mass, difficulty building strength, or mood changes can be related to low free testosterone even when total testosterone looks normal.

What to watch for

  • Low energy, persistent fatigue, or decreased motivation
  • Reduced sexual desire or erectile changes in men
  • Loss of muscle mass or difficulty gaining strength
  • Mood changes such as increased low mood or irritability
  • In women, less androgen excess symptoms like acne or unwanted hair may occur with higher SHBG

Genetic interpretation for rs6259

2 effect alleles (AA) — highest SHBG, lowest free testosterone

The AA genotype is associated with the highest SHBG levels. More testosterone will be bound in the blood and less will be free and active. This may protect against androgen excess symptoms like acne or hirsutism. However, it can also contribute to symptoms related to low free testosterone such as low libido, low energy, reduced muscle mass, and mood changes. Because total testosterone may appear normal, consider testing both total and free testosterone if you notice symptoms.

Considerations

  • Request both total and free testosterone tests when discussing symptoms with your provider
  • Focus on lifestyle supports that help maintain healthy free testosterone
  • Monitor symptoms over time and recheck labs as directed by your clinician
1 effect allele (AG) — intermediate SHBG, reduced free testosterone relative to typical

The AG genotype is linked to intermediate SHBG levels. You may have somewhat less free testosterone compared to typical levels. This can contribute to milder forms of the same symptoms seen with the AA genotype, including fatigue, lower libido, and modest reductions in muscle mass. In women, modestly higher SHBG can reduce androgen excess symptoms but may affect energy or mood if free testosterone is low.

Considerations

  • Test both total and free testosterone if symptoms arise
  • Support hormone balance with targeted lifestyle strategies
  • Talk with your clinician about whether further evaluation is needed
0 effect alleles (GG) — typical SHBG, normal free testosterone availability

The GG genotype is associated with typical SHBG levels. You are likely to have a normal proportion of testosterone circulating in its unbound, active form. That supports standard energy, mood, muscle mass, and metabolic function. Maintain healthy habits to preserve optimal hormone balance.

Considerations

  • Routine monitoring only as clinically indicated
  • Maintain lifestyle habits that support healthy hormone levels
  • See your healthcare provider if you develop symptoms

Practical steps to support healthy free testosterone

Diet and nutrition

  • Prioritize adequate protein intake to support muscle mass and hormone production. Aim for a protein source at each meal.
  • Include healthy fats such as olive oil, avocados, nuts, seeds, and fatty fish to support steroid hormone synthesis.
  • Keep carbohydrate intake balanced around activity to support training and recovery. Whole grains, legumes, and vegetables are good choices.
  • Maintain a nutrient-dense diet including zinc rich foods like oysters, beef, pumpkin seeds and selenium sources such as Brazil nuts, which support reproductive hormones.
  • Avoid highly processed foods and excessive alcohol, both of which can negatively affect hormones and liver function.

Supplements to consider discussing with your provider

  • Vitamin D if levels are low. Low vitamin D has been linked to lower testosterone in some people.
  • Zinc when dietary intake is insufficient. Zinc plays a role in testosterone production.
  • Magnesium for sleep and recovery support which can indirectly benefit hormone balance.
  • Omega 3 fatty acids for overall metabolic and inflammatory support.
  • Only start supplements after checking labs and discussing safety and dosing with your healthcare provider.

Exercise and body composition

  • Resistance training 2 to 4 times per week helps preserve or increase muscle mass and can support testosterone function.
  • Include compound movements like squats, deadlifts, presses and rows for maximal hormonal and strength benefits.
  • Moderate intensity aerobic activity supports metabolic health. Avoid chronic excessive endurance training without adequate recovery as that can lower testosterone.
  • Maintain a healthy body composition. Both excess body fat and very low body fat can negatively affect hormones.

Sleep and stress management

  • Aim for consistent sleep of 7 to 9 hours per night. Poor sleep lowers testosterone and increases SHBG in some people.
  • Practice stress reduction techniques such as mindfulness, breathing exercises or short walks to reduce chronic cortisol elevation which can disrupt hormones.

Limit exposure to hormone-disrupting chemicals

  • Reduce use of plastics for food storage especially when heating. Prefer glass or stainless steel.
  • Choose personal care products and cleaning items with fewer synthetic fragrances and known endocrine disruptors.
  • Avoid unnecessary exposure to known pesticide residues by washing produce and choosing organic where feasible.

Testing and monitoring

If you experience symptoms suggestive of low free testosterone, discuss testing with your healthcare provider. Useful tests may include total testosterone, free testosterone or calculated free testosterone, SHBG, luteinizing hormone, prolactin, thyroid tests, vitamin D, and basic metabolic panels. Results should be interpreted in the context of symptoms, health history, and other lab values.

Final notes and disclaimer

PlexusDx provides educational information about genetic predispositions. This content is not medical advice. Always consult your healthcare provider before making medical decisions, starting new supplements, or changing your treatment plan.

If this genetic variant is present in your PlexusDx results, the following tests and reports are commonly used to explore it further:

🧬 Genetic Tests:

🧪 Blood Tests:

📄 Genetic Report:

Frequently Asked Questions About Testosterone and SHBG rs6259

How does the SHBG rs6259 variant affect free testosterone and symptoms?

SHBG is made by the liver and binds testosterone, so higher SHBG typically means less free (active) testosterone. The rs6259 variant can influence SHBG levels: AA is linked to the highest SHBG and lowest free testosterone, AG to intermediate SHBG, and GG to typical SHBG. Because symptoms may reflect free testosterone rather than total testosterone, you could notice issues like low energy, reduced libido, mood changes, or muscle loss even if total testosterone appears normal.

Should I test both total testosterone and free testosterone if I have rs6259?

Yes—if you have symptoms that could relate to low free testosterone, it’s often useful to request both total testosterone and free testosterone (or calculated free testosterone) plus SHBG. This is especially important because two people can have the same total testosterone but different free testosterone depending on SHBG. Your clinician may also consider additional labs such as luteinizing hormone, prolactin, thyroid testing, vitamin D, and basic metabolic panels to interpret results in context.

What lifestyle steps can support healthy free testosterone with the rs6259 genotype?

Focus on habits that help hormone balance regardless of genotype, including: eating enough protein and healthy fats to support steroid hormone synthesis, keeping carbohydrates balanced around activity, avoiding excessive alcohol and highly processed foods, and getting resistance training 2–4 times per week while avoiding chronic overtraining. Prioritize 7–9 hours of consistent sleep and stress reduction to reduce cortisol-related hormone disruption. You can also discuss potential supplements (such as vitamin D, zinc, magnesium, and omega-3) with your healthcare provider, and limit exposure to hormone-disrupting chemicals (e.g., reducing heated plastic contact with food and choosing products with fewer endocrine disruptors).

What tests can help me learn more about Testosterone and SHBG rs6259?

The Hormone, Thyroid, and Reproductive Health Genetic Test delivers over 85 personalized genetic insights through a comprehensive Hormone & Fertility Genetic Report, explaining inherited tendencies related to hormonal balance, reproductive function, and endocrine signaling. The Womens Hormone and Fertility Health Genetic Report translates your results into personalized, actionable guidance. Your healthcare provider can also recommend targeted blood tests based on your specific pathway results and health history to complement your genetic insights with current biomarker data.