Reptiles and Amphibians Q&A 17

These two adult Galapagos tortoises were fed a diet of mixed vegetables, with a preponderance of cabbage, for over one year. All the tortoises within the collection who were fed the same diet display similar lesions.

Question	Answer		Article
What is your diagnosis?	Hypothyroidism leading to the formation of fibrous goitres.		Link to Article
What causes this condition?	In this instance, the feeding of a diet consisting mostly of cabbage (which contains goitrogens) induces diminished function of the thyroid gland and its synthesis and secretion of thyroxin. This is a condition common to herbivorous reptiles that have evolved in volcanic island habitats in which halogen- (iodine, chlorine, fluorine and bromine) sequestrating plants predominate over those that do not concentrate halogens in their tissues.		Link to Article
What is the treatment for this disorder?	Administer a source of iodine every five to seven days, eg, sodium- or potassium iodide solution (0.25–0.50mg/kg i/v or orally) or Lugol’s solution (0.5–2.0mg/kg orally).		Link to Article
What measures can be taken to prevent it?	Supplement the diet with kelp tablets; the dosage of this form of iodine is not critical because kelp is essentially non-toxic when used as a dietary supplement for giant tortoises. Depending upon their iodine content, a 150–200kg tortoise could be given three to six tablets weekly.		Link to Article