Sex Hormone Binding Globulin

When high

When SHBG is too HIGH (>50 nmol/L off-cycle):

• Implications: more testosterone bound, less bioavailable free T, potential hypogonadal symptoms despite normal total T
• Common causes: ageing, liver disease, hyperthyroidism, low caloric intake, certain medications
• Boron -- 10mg/day (most evidence-supported supplement; lowers SHBG by ~10% within 1 week)
• Stinging Nettle Root -- 300-600mg/day (may compete with SHBG for hormone binding)
• Magnesium -- 400mg/day (deficiency is associated with higher SHBG)
• Vitamin D3 -- 5000 IU/day (deficiency associated with elevated SHBG)
• Address caloric deficit if dieting -- chronic restriction raises SHBG
• Ensure adequate carbohydrate intake -- very low-carb diets can raise SHBG
• Check thyroid function -- hyperthyroidism elevates SHBG significantly

Pharmacological options (for stubborn high SHBG with hypogonadal symptoms despite normal total T):

• Proviron (Mesterolone) -- 25-50mg/day; DHT-derivative that both binds SHBG and suppresses hepatic SHBG synthesis. Drops measured SHBG 30-50% within 4-6 weeks. Most effective oral option for SHBG management. Side effects: increased free E2 (more testosterone available to aromatise), accelerated hair loss in predisposed individuals, prostate stimulation (monitor PSA), HDL reduction
• Nandrolone (low-dose, on TRT) -- 50-100mg/week; mild SHBG suppression as a secondary benefit when added to TRT. Introduces 19-nor risks (prolactin elevation, progestogenic gyno, sexual dysfunction); requires prolactin monitoring and often cabergoline support
• Anavar (Oxandrolone) -- 10-20mg/day; potent SHBG suppression but significant lipid impact (HDL crash) and mild hepatic strain. Generally not first-line for SHBG management alone; reserved for cycles
• Trade-offs to monitor: lowering SHBG raises free E2 alongside free T, which can paradoxically worsen estrogen sides. Manage E2 in parallel and recheck free T, free E2, lipids, and PSA at 6-8 weeks
• All pharmacological SHBG-lowering interventions require physician oversight and baseline bloodwork (lipids, PSA, liver enzymes, full hormone panel)

When low

When SHBG is too LOW (<10 nmol/L):

• Common on oral AAS (Anavar, Winstrol, Proviron, Dianabol suppress SHBG by 50-90%)
• Implications: rapid testosterone clearance, higher free androgen exposure, more androgenic side effects (acne, hair loss, prostate stimulation), unstable hormone levels between injections
• Recovery: SHBG typically normalises 4-8 weeks after stopping oral AAS
• Tamoxifen -- 10-20mg/day (SERMs raise SHBG via estrogenic hepatic action)
• Increase dietary fibre and reduce refined carbohydrates (insulin resistance lowers SHBG)
• Moderate alcohol consumption raises SHBG (not a recommendation to drink, but explains the mechanism)
• Thyroid optimisation -- hypothyroidism lowers SHBG; ensure TSH/Free T4 are optimal

Clinical context:

• SHBG is produced by the liver and regulated by insulin, thyroid hormones, estrogens, and androgens
• Always interpret total testosterone alongside SHBG and free testosterone
• On TRT/AAS: SHBG is less clinically relevant since exogenous hormones flood the system regardless of binding capacity