You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Iodine is an extremely important element which is required by animals in very small quantities. It forms part of the thyroid hormones and in humans disease due to iodine deficiency in which the thyroid swells (called goitre) was recognised as early as the 3rd millenium BC by the Chinese Emperor Shen-Nung. He apparently recommended seaweed (which does contain iodine) as a treatment for this condition.

Thyroid hormones are responsible for many processes in the body including :

• Normal growth and development
• Regulation of body temperature
• Reproduction
• Muscle activity
• Metabolic processes. 

Basically, thyroid hormones control the rate that cells in the body oxidize substances, and so they control metabolic rate. Indirectly thyroid hormones affect many tissues including :

• Skin and hair
• Physical (skeletal) and mental (brain) development
• The sex organs
• The metabolism of nutrients in food

Too much thyroid hormone (hyperthyroidism) is detrimental, as is too little thyroid hormone (hypothyroidism). Iodine deficiency in the diet leads to inadequate amounts of thyroid hormone production - and so to hypothyroidism. In cats and dogs iodine deficiency is rare unless a "fad" home made diet is being fed. When it does occur a variety of disorders may occur including :

• Goitre (swelling of the thyroid gland in the throat)
• Drowsiness
• Loss of hair (alopecia)
• Mental dullness
• Skin changes
• Skeletal deformities - called cretinism
• Loss of unborn  fetuses in pregnant cats
• Death in cats

"Complete" pet foods contain sufficient iodine and so iodine deficiency is a rare occurrence. Various iodine salt supplements are available to treat affected individuals.

Iodine toxicity is extremely rare as most species can tolerate very high intake without adverse side-effects.

Interestingly, the uptake of iodine by the thyroid gland can be used clinically to treat cancer of the thyroid gland. Radioactive iodine can be given, and this will destroy the cancer cells in the thyroid gland when it is taken up by them. 

Iodine is also a potent antimicrobial agent and it is often used by surgeons as a scrub to clean hands and to wash down the operating site prior to surgery. One disadvantage of this is that, with persistent use, some surgeons develop a skin reaction to the iodine solution.

Updated October 2013