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How SHBG Gene Variants Affect Free Testosterone and What You Can Do

Testosterone plays a central role in muscle mass, libido, mood, energy, and fertility. Most testosterone in the blood is bound to a protein called sex hormone binding globulin, or SHBG. Bound testosterone is inactive; only unbound or "free" testosterone can enter cells and produce biological effects. Genetic variation in the SHBG gene can change how tightly SHBG binds testosterone and therefore how much free testosterone is available. Below is an easy to understand guide to what those genetic differences mean and practical steps you can take to support healthy hormone balance.

Why SHBG matters

SHBG controls the fraction of testosterone that is biologically active. If SHBG binds testosterone more tightly, measured total testosterone may look normal but less will be available to tissues. If SHBG binds less tightly, more free testosterone circulates. Small genetic changes in SHBG can shift this balance and influence symptoms such as fatigue, low libido, reduced muscle mass, and changes in mood or recovery from exercise.

General lifestyle strategies to support healthy free testosterone

  • High-protein diet: Emphasize lean meats, fish, eggs, dairy (if tolerated), and legumes to support muscle and hormone production.
  • Healthy fats: Include sources of monounsaturated and omega-3 fats such as olive oil, avocados, fatty fish, nuts, and seeds to support hormone synthesis.
  • Limit endocrine disruptors: Reduce exposure to plastics containing BPA and phthalates by using glass, stainless steel, or BPA-free containers and avoiding heating food in plastic.
  • Alcohol moderation: Excessive alcohol can lower testosterone and raise SHBG. Keep intake moderate.
  • Prioritize sleep: Aim for 7 to 8 hours of quality sleep each night to support hormone rhythms and recovery.
  • Regular exercise: Combine resistance training to build and preserve muscle with moderate aerobic activity for metabolic health. Avoid excessive endurance training without adequate recovery.
  • Anti-inflammatory diet: Focus on whole foods, vegetables, fruits, and omega-3 rich fish while limiting processed foods and added sugars.
  • Maintain healthy body composition: Excess body fat, especially visceral fat, can alter hormone balance. Strength training and proper nutrition help maintain muscle and healthy fat levels.

Supplements that may help when symptoms are present

Supplements can be supportive when low testosterone symptoms are present, but they are not a substitute for medical evaluation. Always consult your healthcare provider before starting supplements, especially if you take medications or have underlying health conditions.

  • Boron: May modestly increase free testosterone by influencing SHBG and other pathways.
  • Ashwagandha: An adaptogen shown in some studies to support stress resilience and raise testosterone in stressed individuals.
  • Shilajit: A mineral-rich resin used traditionally and studied for potential support of testosterone and energy.
  • Zinc: Essential for testosterone production and often recommended when deficiency is suspected.
  • Vitamin D: Low vitamin D is associated with lower testosterone; correct deficiency through sun exposure, diet, or supplementation as guided by blood testing.

Genetic interpretation: rs6258 (SHBG)

2 effect alleles (TT) — Lower free testosterone

Your genotype: TT for rs6258. This genotype is associated with lower free testosterone. The T allele affects how SHBG binds testosterone, resulting in reduced availability of unbound testosterone even if total testosterone appears normal. This may contribute to symptoms such as fatigue, reduced libido, decreased muscle mass, slower recovery from exercise, or mood changes.

Recommendations

  • Diet: Emphasize high-protein meals with lean meats, fish, eggs, legumes, and healthy fats to support hormone production and muscle maintenance.
  • Reduce exposure to plastics and synthetic chemicals: Use glass or stainless steel for food and drinks; avoid microwaving plastics.
  • Limit alcohol and quitting or reducing heavy drinking can improve hormone balance.
  • Sleep: Prioritize consistent 7 to 8 hours nightly and maintain a sleep routine.
  • Exercise: Focus on regular resistance training 2–4 times per week plus moderate cardio; allow adequate recovery to avoid chronically elevated cortisol.
  • Anti-inflammatory habits: Increase vegetables, fruits, omega-3 fats and reduce processed foods and added sugars.
  • Supplements: Consider boron, ashwagandha, shilajit, zinc, and vitamin D if you have symptoms. Consult your healthcare provider for personalized dosing and to check for interactions.
  • Testing: If symptomatic, speak to your provider about measuring total testosterone, free testosterone, SHBG, vitamin D, and zinc status to guide interventions.
1 effect allele (CT) — Likely lower free testosterone

Your genotype: CT for rs6258. Carrying one T allele means you are likely to have somewhat lower free testosterone compared to people without the T allele. This can mean that total testosterone looks normal while the free fraction is reduced, which may affect energy, mood, libido, and muscle maintenance.

Recommendations

  • Diet: Prioritize adequate protein from lean meats, fish, eggs, dairy (if tolerated), and plant proteins. Include healthy fats for hormone synthesis.
  • Environmental factors: Minimize exposure to BPA and phthalates by choosing safer containers and personal care products.
  • Alcohol and sleep: Keep alcohol moderate and maintain 7–8 hours of quality sleep per night.
  • Exercise and inflammation: Regular resistance training plus an anti-inflammatory diet will support free testosterone and overall health.
  • Supplements: Boron, ashwagandha, shilajit, zinc, and vitamin D may be helpful when symptoms occur. Confirm with your healthcare provider before starting.
  • Monitoring: Talk to your healthcare provider about testing free testosterone and SHBG if you have relevant symptoms.
0 effect alleles (CC) — Typical SHBG function

Your genotype: CC for rs6258. This typical genotype is associated with normal SHBG binding function and expected free testosterone availability. With typical SHBG function, free testosterone levels are more likely to reflect normal hormone activity that supports muscle mass, libido, energy, and mood.

Recommendations

  • Maintain a balanced, high-protein diet and adequate healthy fats to support hormone production.
  • Continue limiting exposure to endocrine-disrupting chemicals, moderate alcohol, and prioritize 7–8 hours of sleep nightly.
  • Engage in regular resistance training and cardiovascular exercise, and follow an anti-inflammatory eating pattern.
  • Consider routine checks of vitamin D and zinc and supplement only if deficient or advised by your provider.
  • Maintenance: If symptoms appear, discuss testing of total and free testosterone and SHBG with your healthcare provider to identify potential non-genetic causes.

When to talk to your healthcare provider

  • If you have persistent symptoms such as low libido, fatigue, muscle loss, or mood changes that affect daily life.
  • If you are considering hormone replacement or prescription therapies to address low testosterone.
  • Before starting any new supplement, especially if you take medications or have chronic health conditions.
  • To get lab tests such as total testosterone, free testosterone, SHBG, vitamin D, and zinc to guide targeted care.

PlexusDx provides education about genetic predispositions and lifestyle strategies to support wellness. PlexusDx does not provide medical advice. Always consult your healthcare provider before making changes to your medications, supplements, or treatment plans, or if you have concerns about your hormone health.