Effects of low dose oral iodide supplementation on thyroid function in normal men

Area of Science:

• Endocrinology
• Nutritional Science
• Thyroid Research

Background:

• Previous research indicates high-dose oral iodide inhibits thyroid hormone secretion.
• Iodide intake in the USA can be substantial, potentially affecting thyroid function.
• The effects of very low-dose iodide supplementation require further investigation.

Purpose of the Study:

• To investigate the impact of very low-dose iodide supplementation on thyroid function in healthy men.
• To determine dose-related effects of iodide on thyroid hormone levels and TSH response.
• To assess changes in serum and urinary iodide concentrations.

Main Methods:

• Thirty healthy men (aged 22-40) received 500, 1500, or 4500 micrograms of iodide daily for two weeks.
• Serum samples were analyzed for T4, T3, TSH, protein-bound iodide (PBI), and total iodide.
• Urinary iodide excretion and TRH tests were performed before and after supplementation.

Main Results:

• Significant dose-related increases in serum total and inorganic iodide and urinary iodide excretion were observed.
• Serum T4 and free T4 index decreased significantly at 1500 and 4500 micrograms/day iodide doses.
• A significant increase in TSH response to TRH occurred at 500 micrograms/day, with further increases in basal and stimulated TSH at higher doses.

Conclusions:

• Very low-dose iodide supplementation can alter thyroid hormone levels and TSH secretion in healthy men.
• These findings suggest that current high iodide intake levels may impact thyroid function.
• Further research is needed to understand the long-term implications of iodide supplementation on thyroid health.