A low Total Testosterone (TT) reading is only the starting point for a hypogonadism diagnosis. To truly understand the clinical status of low T, your Canadian physician must assess the amount of biologically active, or “free,” testosterone available to your body’s cells. This requires a close examination of Sex Hormone Binding Globulin (SHBG).
When testosterone is released into the bloodstream, it doesn’t float around on its own. It quickly binds to proteins. These bindings determine whether the hormone is available to your body’s tissues:
The combination of the Albumin-bound and Free Testosterone is known as Bioavailable Testosterone. For practical purposes, Free Testosterone is the most critical number for determining clinical symptoms.
SHBG acts like a sponge in your bloodstream, soaking up testosterone and preventing it from being used. Therefore, high SHBG levels can cause symptoms of low T, even if your Total Testosterone is in the mid-to-high range.
Factor | Mechanism | Clinical Impact |
Aging | SHBG levels naturally increase with age. | A major reason why older men with normal TT still experience low T symptoms. |
Thyroid Issues | Hyperthyroidism (overactive thyroid) significantly raises SHBG. | Often requires treating the underlying thyroid issue before addressing T. |
Liver Disease | Chronic liver conditions can alter protein synthesis. | Can lead to highly elevated SHBG. |
Low-Dose TRT Gels | Transdermal delivery can sometimes increase liver SHBG production. | Requires more frequent monitoring of FT. |
Factor | Mechanism | Clinical Impact |
Obesity/High Insulin | Excess insulin is a key inhibitor of SHBG production in the liver. | A very high TT may result in abnormally high FT, even when TT is only moderately high. |
Hypothyroidism | An underactive thyroid can reduce SHBG levels. | Often seen in conjunction with other low T symptoms. |
High Doses of Androgens | Anabolic steroids or high-dose TRT will suppress SHBG. | Contributes to the “super-physiological” effects often seen with steroid cycles. |
Due to technical difficulties and cost, direct measurement of Free Testosterone in a lab is often inaccurate. Instead, a calculated value is used, requiring three blood markers:
A calculation, often using the Vermeulen equation, provides the most reliable estimate of the patient’s true FT level.
Scenario | TT Level | SHBG Level | FT Level | Clinical Interpretation |
True Hypogonadism | Low | Normal | Low | Problem is low production (Primary or Secondary Hypogonadism). |
High SHBG Low T | Normal/High | High | Low | The sponge is soaking up too much T; symptoms are SHBG-driven. |
Low SHBG Low T | Low | Low | Low | A complicated case, often seen with metabolic issues (insulin resistance). |
If your Total T is in the 12-15 nmol/L range but your FreeT is below 0.2 nmol/L, you are a symptomatic candidate for TRT, even with a “normal” Total T reading. The Free T metric is the better predictor of androgen deficiency symptoms.
For a complete breakdown of target ranges, clinical implications, and how to track all these markers: Blood Work Explained: Reading Your Total T, Free T, SHBG, and Lipid Panel