Hello, lovelies!
Let’s talk about SHBG, or as I unfairly, yet lovingly, call it: “the little gremlins” of the hormone world.
Why?
Because these sneaky little saboteurs can mess up the delicate balance of your hormones faster than you can say “what happened to my libido?!”
Buckle up, because we’re about to dive into why Sex Hormone-Binding Globulin (SHBG) can feel like your body’s mischievous hormone gatekeeper—
and how it impacts your testosterone, oestrogen, and progesterone.
What Even Is SHBG?
SHBG is a protein made by your liver that binds to sex hormones—testosterone, oestrogen, and to a lesser extent, progesterone.
Once a hormone is bound to SHBG, it becomes inactive, like a celebrity stuck behind a velvet rope.
Only free hormones (those not bound to SHBG) can actually get into cells and do their jobs. SHBG is essentially a bouncer deciding how many hormones can enter the party—and spoiler alert—it can be overly strict.
The Tricky Balance
Here’s where it gets complicated:
SHBG levels are influenced by hormones themselves.
Yep, hormones love to meddle in their own regulation. Let me give you the rundown:
Increases SHBG:
Oestrogen: It’s the star player when it comes to ramping up SHBG production.
This is why oestrogen-dominant states (hello, pregnancy or birth control pills) can spike your SHBG.
Progesterone: Surprise! Oral micronized progesterone can also increase SHBG, though less dramatically than oestrogen.
Thyroid Hormones: Hyperthyroidism, anyone?
Liver Health: A happy liver = more SHBG.
Decreases SHBG:
Testosterone: The bad boy of hormones likes to suppress SHBG. That’s why high testosterone levels = more free testosterone.
Insulin: High insulin (thanks, PCOS or insulin resistance) can lower SHBG, leading to more free androgens (testosterone).
Obesity: Higher body fat tends to reduce SHBG.
Cortisol: Stress, ladies. It gets us every time.
My SHBG Saga
Now, here’s where things get juicy (and personal).
After entering surgical menopause for PMDD, I initially used only oestrogen and testosterone add-back therapy.
I was blessed with a low SHBG, perhaps as I never used birth control
(apart from a very brief and deadly stint!)
That’s for another post! Progestins and I are not friends!
I avoided progesterone like the plague because I was told it was the root cause of my PMDD.
Sounds logical, right? Well…not quite. But that’s also a story for another day
(hint: stay tuned for another ranty post).
I recently started dabbling in progesterone therapy again—testing the waters, dipping my toes in and out.
However, I noticed something odd: my testosterone therapy wasn’t working, and I felt like my oestrogen had collapsed.
Did my hormone levels actually plummet?
Nope! It turns out progesterone had doubled my SHBG, which tanked my free testosterone and caused a ripple effect on my free oestrogen.
How Does This Happen?
Picture SHBG as an overzealous librarian: when it doubles, it snatches up all your free hormones and shelves them where they can’t be used. Specifically:
Testosterone: SHBG swoops in and binds more testosterone, dramatically reducing your free testosterone.
Low free testosterone = less energy, reduced libido, and overall “meh” vibes.
Oestrogen: The knock-on effect means your free oestrogen also takes a hit, leaving you feeling like your hormone therapy isn’t working—even if total levels look fine on a blood test.
Testing SHBG (and Why You Must Do It!)
If you’re relying solely on blood tests for total hormones, you’re missing the bigger picture.
In the UK, we don’t measure free oestrogen, so SHBG becomes our surrogate detective.
A good consultant will test your SHBG levels and interpret your free hormone profiles.
In the USA, they’re lucky enough to test actual free estradiol levels, but in the UK, we calculate free testosterone using your total testosterone and SHBG.
The results help determine whether you’re getting enough free hormones for your body to thrive.
Free Testosterone: The Magic Number
The UK defines “normal” free testosterone for women here.
However, I’ve learned through years of trial, error, and hundreds of blood tests –
that I need my free testosterone at above the higher end to feel well.
Each to their own but don’t feel boxed in!
Many women find that the “normal range” is too conservative and doesn’t reflect their actual needs.
Why?
Because these ranges are based on averages, not optimal health.
Free Testosterone Calculator: Want to see where your free T falls?
Use this free testosterone calculator and plug in your total T, SHBG, and albumin levels.
Arm Yourself with Knowledge
Ask for SHBG Testing:
If you’re still symptomatic on what’s considered “reasonable” hormone dosing,
check your SHBG.
High SHBG might mean you’re not getting enough free hormones.
Understand Free T & E:
Don’t let “normal” ranges gaslight you into thinking you’re fine if you’re still feeling rubbish.
You know your body best.
Advocate for Yourself:
If your consultant doesn’t test SHBG or free testosterone, push for it—or find one who will.
You deserve proper care!
Wrapping It Up
SHBG is tricky.
It’s not inherently evil, but it’s definitely a wildcard that can mess with your hormone therapy if you’re not paying attention.
Know your levels, know your body, and don’t let the little gremlins win. 💪
Let’s keep this conversation going, lovelies—drop your SHBG stories below! ✨
Further reading –
Sex Hormone Binding Globulin (SHBG) – Chemical Pathology
Sex hormone-binding globulin and arthritis: a Mendelian randomization study
