Serum vitamin D levels and hypogonadism in men.

Plain-language summary

This study looked at whether vitamin D levels track with testosterone, and with hypogonadism (when the testicles do not make enough testosterone, which shows up as low drive, fatigue and lost muscle), in men. It measured vitamin D, total testosterone and SHBG (sex hormone-binding globulin, a protein that binds testosterone in the blood and holds it out of use, so higher SHBG means less testosterone free and usable) in 225 middle-aged men and compared testosterone across vitamin D ranges. Across the group there was no link between vitamin D and testosterone. Men at the very top of the vitamin D range had more low testosterone, and men at the very bottom showed the same trend without a significant change. The authors read this as a U shape, with the middle of the range looking best. A second study here, a randomized trial of vitamin D supplements, comes from the same Graz research group using a different group of men.

Key findings

• No significant link between vitamin D and testosterone levels overall.
• Men with very high vitamin D (>102 nmol/L) had a higher risk of hypogonadism.
• Men with very low vitamin D (≤43.9 nmol/L) showed a trend toward higher risk of hypogonadism.
• Optimal vitamin D levels for testosterone health may be 82-102 nmol/L.