Scaled Testosterone: A Novel Metric to Calibrate Serum Testosterone and SHBG in Men

Plain-language summary

This study built a better way to read testosterone in men, especially men with obesity, by accounting for SHBG (sex hormone-binding globulin, a protein that binds testosterone and sets how much is free and usable). Pooling data from more than 10,000 men across three Australian studies, the researchers created a measure called Scaled Testosterone that compares testosterone and SHBG directly and sidesteps the unreliable 'free testosterone' math. They found that in obese men a low testosterone reading usually comes with a low SHBG, a pattern they call pseudo-hypogonadism of obesity (a low reading driven by low SHBG rather than a true failure of the testicles). The measure held steady as men lost weight, suggesting the low number was not a real hormone disorder.

Key findings

• Scaled Testosterone (ST) compares standardized testosterone and SHBG levels without relying on free testosterone fractions.
• In obese men, low testosterone is proportionate to low SHBG, suggesting pseudo-hypogonadism rather than true hypogonadism.
• ST remained within standard limits during diet-induced weight loss in obese men.