Equine goiter associated with excess dietary iodine.

This research article discusses a case study of newborn Arabian horses developing goiter because their mothers were given too much iodine during the final weeks of pregnancy. The excess iodine also affected other nursing foals and mares.

About the Research Study

• This study focuses on naturally occurring cases of goiter observed in newborn Arabian foals. The term ‘foal’ is used to refer to a young horse, and ‘goiter’ is a condition usually characterized by the abnormal enlargement of the thyroid gland.
• The main cause of goiter in this situation was found to be excessive consumption of iodine by the foals’ mothers, specifically during the last 24 weeks of their pregnancy.

Details About the Iodine Overdose

• The amount of iodine consumed by the mares considerably exceeded the tolerable dietary levels. Specifically, at least twelve times more than the accepted limit was ingested, with the daily intake for each mare averaging at 299 mg.
• Six nursing foals and two mares also showed symptoms of thyroid hypertrophy, which is an increase in size or swelling of the thyroid gland, a common indication of iodine overdose in horses.

Prevalence of Goiter

• The recorded prevalence of these goiter cases amongst the mares was relatively low, at 2%. This figure suggests that the occurrence of goiter due to excess iodine supplementation is less frequent amongst adult horses.
• However, the prevalence of goiter was higher amongst the foals, at 9%. This suggests that while adult horses may largely resist the effects of iodine overdose, their foals may not have the same level of resilience, leading to a higher incidence of iodine-induced goiter when the mothers have an excessive intake.