What Effects do Vitamin D, Statins Have on Testosterone Levels in Men?

New research indicates that an over-the-counter supplement doesn’t raise testosterone levels but a widely used class of prescription drug may lower them.

Health-and-fitness publications have long claimed that large doses of vitamin D can make the body produce more testosterone, and some studies have found small-but-significant increases, but a new analysis reaches the opposite conclusion.

Researchers took data from 3 trials that randomly assigned184 men of different ages and ethnic backgrounds to receive either 25-hydroxyvitamin D or placebo. Vitamin D doses ranged from 600 IU per day to 2,000 IU per day and trial durations ranged from 6 weeks to 16 weeks.

Blood was drawn from all patients at baseline, the halfway mark of each trial and at the end of each trial. Serum 25-hydroxyvitamin D levels were measured using LC-MS/MS or radioimmunoassay. Testosterone levels were measured using a second-generation immunoassay.

Vitamin D levels held steady in all 3 of the control groups but increased in all 3 of the study groups. Median increases ranged from 27 nmol/L to 36 nmol/L. Testosterone levels, however, did not increase significantly — not even among men who began trials with vitamin D deficiencies.

The authors of the paper, which appears in Clinical Endocrinology, noted that none of the trials were particularly large or particularly long and then made their conclusion.

“In this post-hoc analysis of 3 small clinical trials of limited duration in men with normal baseline testosterone concentrations, vitamin D supplementation was not associated with an increase in circulating testosterone concentrations,” they wrote.

Statins, on the other hand, may well have a significant effect on testosterone concentrations — a significant negative effect.

Researchers in Poland searched hospital records for a representative sample of statin-using men and then compared their testosterone levels with those of statin-free men who were otherwise similar.

Even after controlling for potential confounders such as body mass, the results were significant. Statin-users had lower concentrations of total testosterone (14.9 vs. 16.35 nmol/L, p = 0.008), free testosterone (32 vs. 39 pmol/L, p = 0.004), calculated free testosterone (0.32 vs. 0.36 nmol/L, p < 0.001) and bioavailable testosterone (6.10 vs. 7.56 nmol/L, p < 0.001).

The study team noted several limitations in its work, limitations that included both the study’s retrospective nature and the inability to determine whether the statins or the health problems that necessitated their use (or some other factor) accounted for the differences in testosterone.

Still, the researchers argued that statins may well be the culprit and that further research is justified.

“We conclude that the use of statins may have an impact on the diagnosis of age-related testosterone deficiency in men,” they wrote in Endokrynologia Polska.

Other researchers have reached similar conclusions about statins. For example, a study of 3,484 men with erectile dysfunction found that men who were using statins when the study took place were twice as likely as other men to suffer clinical hypogonadism.

Not all studies have found such a link between statins and testosterone, however, and some research suggests that statins may ameliorate erectile dysfunction, not because it boosts testosterone but because it reduces some of the cardiovascular problems that produce erectile dysfunction.

Still, with regulators around the world asking what constitutes “normal” testosterone levels for older men and what constitutes “below normal” concentrations of the hormone, it could be important to determine whether the widely used medications are depressing testosterone in millions of men.