Skip to main content
Iodine Linked With Men's Testosterone Levels
Courtesy: medpagetoday


In a groundbreaking cross-sectional study involving nearly 3,000 U.S. men, researchers at the University of L’Aquila in Italy uncovered a surprising connection between urinary iodine concentrations and testosterone levels. This article delves into the intricacies of this association, challenging traditional notions about iodine’s harmlessness and shedding light on potential health implications.

Understanding the Study Parameters

1. Study Sample and Demographics

The investigation comprised 2,934 men with a mean age of 47.1, drawn from five cycles of the National Health and Nutrition Examination Survey spanning from 1999 to 2002 and 2011 to 2016.

2. Testosterone Measurement Techniques

Testosterone levels were meticulously measured using isotope dilution high-performance liquid chromatography-tandem mass spectrometry, ensuring accuracy in the findings.

3. Iodine Concentration Categories

Participants were categorized based on urinary iodine concentrations: low (under 100 μg/L), normal (100-299 μg/L), and high (300 μg/L or over).

The Astonishing Findings

4. Testosterone Disparity Across Iodine Categories

Men with lower urinary iodine concentrations exhibited significantly higher total testosterone levels compared to their counterparts with normal or high iodine levels.

5. Numerical Representation of Testosterone Levels

Median total testosterone levels for the low iodine category were 446.70 ng/dL, contrasting with 398.68 ng/dL and 398.50 ng/dL in the normal and high categories, respectively.

6. Correlation with Free Testosterone

Similar trends were observed in calculated free testosterone levels, with values of 75.80 pg/mL, 72.10 pg/mL, and 67.20 pg/mL for low, normal, and high iodine categories, respectively.

Possible Mechanisms and Implications

7. Interaction Between Iodine, Thyroid Hormones, and Testosterone

The researchers explored the intricate interplay between iodine intake, thyroid hormones, and testosterone. While not definitively ruling out an interaction, they suggested that excess iodine might directly impact testicular steroidogenesis.

8. Insights from Animal Models

The study aligns with prior preclinical animal models, wherein rats on a high-iodine diet exhibited testicular iodine accumulation, triggering oxidative stress and inhibiting testosterone activity.

9. Surprising Revelations and Health Implications

Lead researcher Arcangelo Barbonetti expressed surprise at the findings, emphasizing that excess iodine, traditionally considered harmless, could potentially lead to health issues, including androgen deficiency.

Practical Considerations and Recommendations

10. Thyroid Dysfunction and Iodine Categories

Men with lower iodine concentrations also showed the lowest levels of thyroid dysfunction, though the differences were not statistically significant.

11. Cautionary Notes for Iodine Prophylaxis

Barbonetti’s group urged caution in medical therapies or diagnostic procedures introducing iodine loads, especially in iodine-sufficient countries. They called for a reconsideration of the mode and extent of iodine prophylaxis.

12. Geographical Variances in Iodine Sufficiency

Regulatory agencies were alerted to the achieved iodine sufficiency in most countries, emphasizing the potential for excessive iodine exposure in specific geographical areas.

Analyzing Participant Characteristics

13. Youthfulness and Metabolic Profiles

Men with lower urinary iodine concentrations tended to be younger and exhibited better metabolic and glycolipid profiles, including a lower BMI.


In redefining our understanding of iodine’s impact, this study prompts a reconsideration of established norms. Excess iodine, once deemed harmless, is now associated with potential health risks, necessitating a cautious approach in medical practices.