Effect of fatiguing bicycle exercise on thyroid hormone and testosterone levels in sedentary males supplemented with oral zinc

Neuro Endocrinol Lett. 2007 Oct;28(5):681-5.


Objective: The aim of this study was to determine how exercise affects thyroid hormones and testosterone levels in sedentary men receiving oral zinc for 4 weeks.

Methods: The study included 10 volunteers (mean age, 19.47+/-1.7 years) who did not exercise. All subjects received supplements of oral zinc sulfate (3 mg/kg/day) for 4 weeks and their normal diets. The thyroid hormone and testosterone levels of all subjects were determined at rest and after bicycle exercise before and after zinc supplementation.

Results: TT3, TT4, FT3, and total and free testosterone levels decreased after exercise compared to resting levels before supplementation (p<0.01). Both the resting and fatigue hormone values were higher after 4 weeks of supplementation than the resting and fatigue values before supplementation (p<0.05).

Conclusion: The results indicate that exercise decreases thyroid hormones and testosterone in sedentary men; however, zinc supplementation prevents this decrease. Administration of a physiologic dose of zinc can be beneficial to performance.

Publication types

  • Clinical Trial

MeSH terms

  • Administration, Oral
  • Adolescent
  • Adult
  • Dietary Supplements
  • Exercise / physiology
  • Exercise Test
  • Fatigue / blood*
  • Humans
  • Male
  • Physical Exertion / physiology*
  • Testosterone / blood*
  • Thyroid Hormones / blood*
  • Thyroxine / blood
  • Trace Elements / administration & dosage
  • Triiodothyronine / blood
  • Zinc / administration & dosage
  • Zinc / physiology*


  • Thyroid Hormones
  • Trace Elements
  • Triiodothyronine
  • Testosterone
  • Zinc
  • Thyroxine