SHBG

Why It Matters

SHBG (sex hormone-binding globulin) is a protein produced in the liver that transports androgens and estrogens through the bloodstream. SHBG regulates hormone interaction with target tissues by binding to them, reducing their bioavailability. (source, source) When SHBG levels shift outside the optimal range, the balance between bound and free hormones changes, directly altering how much testosterone and estradiol reach target tissues. This makes SHBG a gatekeeper of hormonal signaling across reproductive, metabolic, and musculoskeletal systems.

Low SHBG: Excess Hormonal Bioavailability

Low SHBG levels are influenced by physiological factors related to liver function, as the liver is responsible for producing this protein. Obesity, poor dietary choices, excessive consumption of refined carbohydrates, and saturated fats all contribute to lower SHBG levels. (source, source)

Potential Performance Impact:

• Increased free androgen levels leading to acne, oily skin, or hirsutism
• Elevated risk of metabolic syndrome and insulin resistance
• Hormonal imbalances that disrupt reproductive health and fertility
• Greater androgenic activity potentially contributing to hair loss or prostate issues

Optimization

Exercise regularly: Aerobic exercise increases SHBG levels, potentially improving hormonal balance and health. (source)

Protocol: Follow a structured training program that exerts your body through multiple resistance and aerobic intensities. This includes a structured aerobic program that ensures at least 150 minutes of moderate intensity (50 to 70% max heart rate) or 75 minutes of high intensity (75% max heart rate or greater) a week and a structured resistance training program with moderate to heavy loads at least twice a week for resistance training. The final set of each resistance training exercise should be taken within two repetitions of failure.

Reduce body fat: Reduction in body fat is associated with increased SHBG levels. (source) Excess adipose tissue impairs liver function and insulin sensitivity, which reduces SHBG production. Reducing body fat may normalize these pathways and raise SHBG. (source)

Protocol: Create a caloric deficit by reducing caloric intake and/or increasing physical activity. Total body fat is best monitored by DEXA scan. Aim for body fat percentage in the optimal range of 10-20% for men and 18-28% for women.

High SHBG: Reduced Hormone Bioavailability

High SHBG levels can stem from physiological factors related to hormonal balance, liver function, and aging. Nutritionally, high intake of dietary fiber and certain plant compounds, such as phytoestrogens, as well as low body weight, low fat mass, and restricted caloric intake may all contribute to elevating SHBG levels. (source, source)

Potential Performance Impact:

• Reduced free testosterone levels, impairing muscle protein synthesis and recovery
• Decreased androgenic stimulus that weakens training-induced adaptations
• Lower estradiol bioavailability affecting bone density and joint health in women
• Blunted hormonal response to training that reduces performance gains over time

Optimization

Increase body weight: Intentional increases in body weight are associated with decreases in SHBG. (source) As body weight increases (particularly through muscle mass gain), insulin levels tend to rise, which inhibits hepatic SHBG production. This downregulation increases the availability of free testosterone and estradiol. (source)

Protocol: Achieve a caloric surplus of 250-500 kcal/day to gain lean body mass. Total body weight is best monitored by DEXA scan.

Supplement with boron: Boron supplementation is associated with lower SHBG. (source) Boron inhibits SHBG synthesis in the liver and reduces SHBG-binding affinity. This effectively increases bioavailable testosterone. (source)

Protocol: Supplement with 10 mg of boron daily.