Why SHBG Matters: The Unsung Hero (or Villain) in Your Hormone Health

When most people think about hormone replacement therapy (HRT), the focus tends to land squarely on estrogen, progesterone, and testosterone—and understandably so. These are the headliners in the hormonal symphony of perimenopause and menopause. But tucked backstage is a lesser-known, highly influential player: Sex Hormone-Binding Globulin, or SHBG.

As a hormone specialist, I can confidently say: If we’re not monitoring SHBG, we’re missing a critical part of the picture.

Here's why.

What is SHBG, Anyway?

SHBG is a glycoprotein produced primarily in the liver. Its main job? To bind to sex hormones—especially testosterone and estrogen—and carry them through your bloodstream. But here’s the catch: when a hormone is bound to SHBG, it’s not bioavailable. In other words, your body can’t use it.

So while your labs might show a “normal” level of testosterone or estrogen, the real question is: how much of it is free and active? That’s where SHBG becomes crucial. In fact, only about 1–2% of circulating testosterone is free and biologically active, with the remainder bound to SHBG and albumin (1).

Too High, Too Low… Or Just Right?

When SHBG levels are too high, more hormones are bound, leaving fewer free and active in your body. This can lead to symptoms like fatigue, low libido, brain fog, and loss of muscle mass—even if your total hormone levels look “normal.” This is particularly relevant in women receiving testosterone therapy, where SHBG strongly influences effective dosing and symptom relief (2).

When SHBG is too low, it may result in excess free hormone, which increases the risk for estrogen or androgen dominance, mood swings, acne, or unwanted hair growth (3).

In other words, hormone optimization is a Goldilocks game—and SHBG helps us figure out whether your levels are too high, too low, or just right.

Why HRT Without SHBG Monitoring Is Like Guessing in the Dark

Imagine adjusting a patient’s testosterone dose based only on total levels, without accounting for SHBG. You might keep increasing the dose, frustrated that the patient’s symptoms aren't improving—when in fact, their SHBG is high and binding up most of that hormone.

Conversely, without watching SHBG, you might miss the early signs of excess hormone exposure, increasing long-term risks like endometrial hyperplasia, cardiovascular strain, or insulin resistance.

This is why personalized hormone therapy isn't just about replacing hormones—it’s about understanding how your body is metabolizing and regulating them.

What Affects SHBG?

SHBG is dynamic and can be influenced by many factors:

• Estrogen therapy tends to increase SHBG (4)

• Androgens (like testosterone) tend to lower it

• Thyroid hormones increase SHBG levels—especially in hyperthyroidism (5)

• Insulin resistance and metabolic syndrome decrease SHBG (6)

• Liver health, age, and certain medications also have direct effects

  
  

Monitoring SHBG gives us an insight into both hormone transport and your metabolic health, helping guide safe and effective HRT protocols.

In Summary: SHBG Is a Big Deal (Even If It’s Small and Hard to Pronounce)

At my downtown Boise clinic, we routinely monitor SHBG because it provides vital insight into how your body interacts with and regulates hormones. It allows us to fine-tune hormone therapy so you get the best possible results—balanced mood, restored energy, improved libido, and a better sense of control over your midlife transition.

So next time you see “SHBG” on your lab panel, don’t glaze over. Give it a little nod—it might just be the missing link between “meh” and “amazing.”

References:

1. Goldman, A. L., et al. (2017). The role of sex hormone–binding globulin in testosterone delivery to tissues: Implications for the interpretation of total testosterone measurements. The Journal of Clinical Endocrinology & Metabolism, 102(3), 994–1001. https://doi.org/10.1210/jc.2016-2655

2. Davis, S. R., & Wahlin-Jacobsen, S. (2015). Testosterone in women—the clinical significance. The Lancet Diabetes & Endocrinology, 3(12), 980–992. https://doi.org/10.1016/S2213-8587(15)00284-3

3. Cunningham, G. R. (2009). Testosterone and androstenedione. In De Groot LJ et al. (Eds.), Endotext. MDText.com, Inc.

4. Sex Hormone-Binding Globulin. (2023). Lab Tests Online. Retrieved from https://labtestsonline.org/tests/sex-hormone-binding-globulin-shbg

5. Jorde, R., et al. (2006). Thyroid function and sex hormones in men and women aged 40–79 years. Journal of Clinical Endocrinology & Metabolism, 91(8), 3366–3370.

6. Ding, E. L., et al. (2009). Sex hormone–binding globulin and risk of type 2 diabetes in women and men. New England Journal of Medicine, 361(12), 1152–1163. https://doi.org/10.1056/NEJMoa0804381