SHBG and PCOS: the carrier protein that shapes the picture
SHBG — sex hormone binding globulin — is a protein made mainly by the liver that binds to hormones like testosterone and carries them through the bloodstream. It rarely gets the attention testosterone does, but it changes how a testosterone result should be read, which is why the two are so often measured together.
What this test measures
An SHBG test measures how much of this carrier protein is in your blood. Because SHBG binds testosterone, the amount of it affects how much testosterone is free and active versus bound and held in reserve. A low SHBG can mean more free testosterone even when the total looks unremarkable. Reference ranges vary by lab and assay, so your result is read against the range printed on your own report — there's no universal figure, which is why we don't quote one.
Why it comes up in PCOS care
SHBG is part of the androgen workup because it puts testosterone in context. It's used together with total testosterone to work out the free androgen index, the calculated ratio clinicians often look at alongside the raw numbers. The NHS describes hormone blood tests as part of diagnosing PCOS, and SHBG is one of the pieces that stops a testosterone reading from being taken in isolation. A clinician interprets it as part of the whole picture, never on its own.
Keeping results across years
SHBG can shift over time, so a single value is far less informative than a series. Yet these results are exactly the kind that vanish between clinic systems — filed in one portal, printed once, then forgotten. A personal dated vault keeps your SHBG next to your testosterone results, in order, so the relationship between them is visible across years rather than reconstructed from memory. That's what lets a brief appointment focus on the trend instead of hunting for old letters.
PCOS Diary stores SHBG and testosterone results side by side in a dated lab vault, so their relationship reads as a trend in your doctor-ready PDF.
Common questions
- Why is SHBG measured with testosterone?
- Because SHBG binds testosterone, it influences how much is free and active. Measuring both lets a clinician work out the free androgen index and read your testosterone result in context, rather than from the total alone.
- Is there a normal SHBG number I should aim for?
- There's no single figure to quote — reference ranges vary between labs and assays, and SHBG is interpreted alongside your other results, not against a fixed target. Your report shows the range your lab uses for your sample.