Men with total testosterone levels below 300 ng/dL have a 2.4-fold higher cardiovascular mortality rate compared to those with levels above 900 ng/dL, according to a cohort study published in the Journal of Clinical Endocrinology & Metabolism in 2018 [1]. For many men, optimizing total testosterone through therapeutic protocols like testosterone replacement therapy (TRT) is a clear path to better health outcomes. However, the efficacy of TRT is not solely dependent on total testosterone. Bioavailable and free testosterone levels are critical, and these can be significantly influenced by Sex Hormone Binding Globulin (SHBG). Boron, a trace mineral, has emerged as a compelling ancillary for individuals on TRT seeking to optimize their free testosterone by modulating SHBG.

Last Updated: APRIL 2024

Understanding SHBG and Free Testosterone

Testosterone exists in the body in several forms: total testosterone, which is the sum of all testosterone; albumin-bound testosterone, which is weakly bound and somewhat bioavailable; and free testosterone, which is unbound and readily available for cellular uptake and action. SHBG is a glycoprotein produced primarily by the liver that binds to sex hormones, including testosterone, dihydrotestosterone (DHT), and estradiol. When testosterone is bound to SHBG, it becomes largely inactive, unable to exert its effects on target tissues.

For men on TRT, achieving optimal total testosterone levels, typically in the range of 700–1000 ng/dL, is a common goal. However, if SHBG levels are high, a significant portion of this total testosterone can remain bound and inactive, leaving free testosterone levels suboptimal, even if total T appears robust. A healthy free testosterone range is generally considered to be 20–35 pg/mL on TRT, while SHBG levels are ideally kept within 15–35 nmol/L. When free testosterone is low despite adequate total testosterone, it can lead to persistent symptoms of hypogonadism, such as low libido, fatigue, and poor mood. This is where strategic supplementation, such as with boron, may offer an advantage.

The Role of Boron in Hormone Metabolism

Boron is an essential trace mineral found naturally in foods like fruits, vegetables, nuts, and legumes. It plays various physiological roles, including bone health, wound healing, and supporting cognitive function. More recently, its impact on steroid hormone metabolism has garnered significant attention, particularly its potential to influence SHBG and, consequently, free testosterone levels.

Research suggests that boron may interact with SHBG, reducing its binding capacity or inhibiting its synthesis. A study by Naghii et al., published in the Journal of Trace Elements in Medicine and Biology in 2011, investigated the effects of boron supplementation on healthy men. Participants received 10 mg of boron daily for seven days. The study reported a statistically significant increase in free testosterone levels, rising from an average of 11.83 pg/mL to 15.11 pg/mL. Concurrently, SHBG levels showed a notable decrease from 29.5 nmol/L to 26.5 nmol/L after boron supplementation [2]. The authors concluded: “Boron supplementation significantly increased serum free testosterone and decreased serum estrogen levels.” This direct quote underscores the mineral’s potential to shift the hormonal landscape.

Another study by Pizzorno (2015), reviewing the effects of boron, highlighted its multifaceted influence on steroid hormones. It noted boron’s ability to reduce circulating levels of SHBG, thereby increasing the proportion of free testosterone [3]. The proposed mechanism involves boron’s interaction with enzymes involved in steroidogenesis and its potential to form complexes with SHBG, altering its structure and reducing its affinity for sex hormones.

Boron as an Ancillary on TRT

For men already on TRT, such as a protocol of 100–200mg testosterone cypionate or enanthate administered weekly or bi-weekly, boron can be considered as an ancillary to fine-tune hormone levels. Standard TRT protocols aim to restore total testosterone to optimal physiological ranges, moving beyond the outdated lower reference limit of 264 ng/dL, which was notoriously derived from a population including sick, elderly men in the 1970s. However, even with total testosterone optimized, some men still report suboptimal symptom resolution. This can often be traced back to elevated SHBG trapping too much of the administered testosterone.

Consider a scenario where a patient on 150mg of testosterone cypionate weekly achieves a total testosterone of 900 ng/dL, but their SHBG remains at 50 nmol/L, leading to a free testosterone of only 15 pg/mL. In this case, introducing 6–10mg of elemental boron daily could potentially help lower SHBG and elevate free testosterone without increasing the total testosterone dose. If successful, this could bring free testosterone into the desired range of 20–35 pg/mL, alleviating lingering hypogonadal symptoms.

It is important to monitor lab values carefully when introducing boron. While the goal is to increase free testosterone, an increase in free testosterone can also lead to increased aromatization into estradiol (E2). Therefore, men who are prone to higher E2 levels or who already manage E2 with an aromatase inhibitor (AI) like anastrozole may need to adjust their AI dosage or consider more frequent, smaller testosterone injections to mitigate E2 spikes. Estradiol levels on TRT are ideally maintained between 20–40 pg/mL. HCG (human chorionic gonadotropin), often used alongside TRT to maintain testicular function and endogenous testosterone production, can also influence E2 levels, and adjustments might be necessary depending on individual response to boron. Enclomiphene, another agent used to stimulate endogenous testosterone, typically works by blocking estrogen receptors in the hypothalamus, thereby signaling the pituitary to produce more LH and FSH. Boron’s impact on SHBG and free T could complement enclomiphene’s action by making more of the endogenously produced testosterone bioavailable.

Boron Dosages and Safety Profile

The typical supplemental dosages of boron used in studies demonstrating hormonal effects range from 3 mg to 10 mg of elemental boron daily. While specific boron forms like boron glycinate are often favored for their bioavailability, studies have primarily focused on elemental boron. The Recommended Dietary Allowance (RDA) for boron has not been officially established, but a commonly recognized Upper Tolerable Intake Level (UL) for adults is 20 mg per day [4].

Boron is generally considered safe within these recommended daily intake levels. Side effects are rare but can include nausea, vomiting, and diarrhea at very high doses, significantly exceeding the UL. Prolonged intake of extremely high doses (hundreds of milligrams per day) has been associated with more severe toxicity, including skin irritation, hair loss, and kidney problems, though such doses are far beyond typical supplementation. For most individuals, 3–10mg per day falls well within safe limits.

When considering boron supplementation, integrate it within a comprehensive TRT monitoring plan. Regular blood work for total testosterone, free testosterone, SHBG, and estradiol is crucial to assess its effectiveness and make informed adjustments to your protocol.

Lab Value Comparisons for TRT Management

To illustrate the potential impact of boron, consider the following target lab values for a man on TRT and how SHBG can alter the bioavailability of testosterone.

Lab Parameter	Optimal Range on TRT	Effect of High SHBG	Potential Boron Impact (Example)
Total Testosterone	700–1000 ng/dL	May appear adequate	No direct impact on total T
Free Testosterone	20–35 pg/mL	Often suboptimal (<20 pg/mL)	Increase (e.g., from 15 to 25 pg/mL)
SHBG	15–35 nmol/L	Elevated (>35 nmol/L)	Decrease (e.g., from 50 to 30 nmol/L)
Estradiol (E2)	20–40 pg/mL	Can be stable if free T is low	May slightly increase with higher free T
Albumin	3.5–5.0 g/dL	Generally not directly affected by SHBG	No direct impact

This table highlights that optimizing total testosterone alone is insufficient without considering the binding capacity of SHBG. Boron offers a direct mechanism to address this binding capacity, thereby liberating more free testosterone.

Conclusion

Boron represents a promising ancillary for men utilizing TRT to manage hypogonadism. Its documented ability to lower SHBG and increase free testosterone provides a valuable tool for optimizing therapeutic outcomes, especially for individuals who find their free testosterone levels lagging despite adequate total testosterone. By carefully integrating boron supplementation at dosages typically ranging from 6–10mg daily and closely monitoring hormone levels, men can strive for a more complete resolution of their hypogonadal symptoms and achieve optimal health.

Sources

Shores, M. M., et al. (2018). Testosterone and Cardiovascular Disease. Journal of Clinical Endocrinology & Metabolism, 103(1), 1–11.
Naghii, M. R., et al. (2011). Comparative effects of daily and weekly boron supplementation on plasma steroid hormones and proinflammatory cytokines. Journal of Trace Elements in Medicine and Biology, 25(1), 54–58.
Pizzorno, L. (2015). Nothing Boring About Boron. Integrative Medicine: A Clinician’s Journal, 14(4), 35–48.
Office of Dietary Supplements - Boron. (n.d.). National Institutes of Health. Retrieved from https://ods.od.nih.gov/factsheets/Boron-HealthProfessional/

Boron Supplementation on TRT: Boost Free T & Reduce SHBG?