When men with low testosterone start taking testosterone therapy, their triglyceride (a type of fat in the blood) levels tend to go down—sometimes by almost half—if they started with high levels already. This suggests the therapy might help improve their blood fat numbers.

For men with low testosterone, giving them testosterone therapy may lower their triglyceride-to-HDL ratio by almost 20% in a year — and if their ratio was already really high (above 6), it can drop by more than two-thirds, which is good because high ratios are tied to heart and metabolic problems.

For men with low testosterone, taking testosterone therapy may lower their overall cholesterol by about 7% after a year, but it doesn’t seem to change the 'bad' LDL cholesterol.

For men with low testosterone, taking testosterone therapy may lower their 'good' cholesterol by about 11% after a year, even though it helps other heart and metabolism factors get better.

For men with low testosterone, taking testosterone therapy may slightly lower their blood sugar levels after a year, which could mean their diabetes or blood sugar control gets a little better.

Giving testosterone to men with low levels might help their cholesterol and fats in the blood get better, but we still don’t know if that actually makes their heart safer or not.