Zinc status and serum testosterone levels of healthy adults.
Level 4 - case-series / case-control
Cross-sectional analysis combined with very small, uncontrolled before-and-after case series
PubMed 8875519 · doi:10.1016/s0899-9007(96)80058-x
What was done
Investigated the relationship between zinc status and serum testosterone across three components: a cross-sectional study in 40 healthy men aged 20 to 80 years measuring cellular zinc (lymphocyte and granulocyte) and serum testosterone; an experimental zinc-restriction study in 4 healthy young men (mean age 27.5 ± 0.5 years) followed for 20 weeks; and an open-label trial in 9 marginally zinc-deficient elderly men (mean age 64 ± 9 years) before and after 3 to 6 months of oral zinc gluconate supplementation (459 µmol/day).
What was found
Cross-sectionally (n = 40), serum testosterone correlated with lymphocyte zinc (r = 0.43, p = 0.006) and granulocyte zinc (r = 0.30, p = 0.03). In young men (n = 4), 20 weeks of zinc restriction reduced serum testosterone from 39.9 ± 7.1 nmol/L to 10.6 ± 3.6 nmol/L (p = 0.005). In marginally zinc-deficient elderly men (n = 9), 6 months of zinc supplementation increased serum testosterone from 8.3 ± 6.3 nmol/L to 16.0 ± 4.4 nmol/L (p = 0.02).
Why it matters
Provides preliminary evidence that marginal zinc deficiency may reversibly lower serum testosterone concentrations in normal young and elderly men.
Limits
The interventional cohorts were extremely small (n = 4 and n = 9) and lacked control or placebo comparison groups. Potential confounders such as overall caloric intake, other micronutrient changes, and blinding were not reported in the abstract.
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