SHBG and 'free testosterone': what the science says about lowering it

What did @michelehormonehealth actually say?

The creator argues you can't lower SHBG directly, you have to fix what's causing it to be elevated in the first place. She points to low insulin signaling, undereating, thyroid dysfunction, estrogen, and oral medications affecting liver metabolism as the common culprits. She mentions supplements like boron, magnesium glycinate or taurate, and vitamin D as having "decent data" but frames them as supporting players, not the main event. She closes with the practical point that if your testosterone reads normal on paper but you feel lousy, elevated SHBG could be binding enough free testosterone to explain the gap.

To her credit, she doesn't promise a fix. She's describing a clinical framework, not a protocol. That's a meaningful distinction in a space full of people selling you the answer before they know the question.

Does the science back this up?

Mostly, yes. The core claim, that SHBG is a downstream marker rather than a primary target, is well-supported. Research consistently shows SHBG rises in response to upstream signals, and treating the number without addressing the cause is a dead end.

On insulin signaling: this is one of the more solid connections in SHBG research. Studies, including work by Goodman-Gruen and Barrett-Connor (1997, Journal of Clinical Endocrinology and Metabolism), showed inverse relationships between insulin resistance markers and SHBG. More recent work by Wallace et al. (2013, JCEM) confirmed that insulin suppresses hepatic SHBG production directly. The thyroid connection is also legitimate. Hyperthyroidism raises SHBG; hypothyroidism tends to lower it. Plymate et al. (1985, JCEM) documented this relationship clearly.

On oral estrogens affecting liver SHBG production: this is accurate. First-pass hepatic metabolism from oral estradiol raises SHBG significantly more than transdermal routes. That's a clinically relevant distinction, particularly for perimenopausal patients on hormone therapy.

On supplements: boron has some data (Naghii and Samman, 1997, Environmental Health Perspectives showed modest effects on sex hormone levels), but the effect sizes are not large. Magnesium has indirect mechanistic plausibility through insulin sensitivity, but direct SHBG-lowering evidence is thin. Vitamin D research here is mixed. She appropriately hedges with "decent data" rather than overclaiming.

What did they get wrong (or right)?

She gets the framework right. The critique that people try to lower SHBG directly is a fair observation about how patients often approach this online, and her redirection toward root causes is clinically sound.

Where the video is thin: she mentions "estrogen, rut like oral and liver metabolism" in a way that's clearly garbled in the transcript, likely a recording artifact, but it points to a real gap. The nuance that oral estrogen raises SHBG while transdermal estrogen does not to the same degree is important clinical information that doesn't fully land here. Patients on oral estradiol or oral contraceptives dealing with SHBG issues need to know the route of administration matters, not just the hormone class.

She also lumps magnesium glycinate and taurate together as roughly equivalent options without distinguishing them. These are different forms with different absorption profiles. The "glycerate" mentioned appears to be a verbal slip for glycinate. It's a small error, but in a medical context, form matters.

No dangerous claims are made. No dosing is prescribed. The supplement recommendations are hedged appropriately. For a TikTok video under two minutes, this is more responsible than most in this category.

What should you actually know?

SHBG is produced in the liver, and almost everything that raises or lowers it does so by changing liver signaling. That's why oral medications, metabolic status, thyroid function, and nutritional state all matter. If your free testosterone is low because SHBG is high, the question is always: why is SHBG elevated in the first place?

The free testosterone calculation itself deserves scrutiny. Most labs report calculated free testosterone, not directly measured free testosterone. The Vermeulen calculation, which is commonly used, has known accuracy limitations depending on the albumin value used. If you're making clinical decisions based on this number, it's worth knowing how your lab derived it.

Boron supplementation has legitimate but modest supporting evidence. Do not expect dramatic SHBG reductions from supplements alone if you have significant metabolic dysfunction, thyroid disease, or are on oral hormones driving the elevation. Fixing the driver matters more than any single supplement. Talk to a clinician who will actually measure your full hormone panel, not just total testosterone.