The thyroid gland, located in the neck region, has been observed to enlarge due to proliferation of epithelial cells in the follicles in many species of birds, including pigeons, canaries, budgerigars, and wild birds.
Several conditions are known to damage the thyroid gland. The most common is dietary iodine deficiency. An inadequate level of
iodine in the diet leads to a lack of available iodine in the thyroid
glands. Iodine is needed for the production of thyroxine. When low
levels of thyroxine are in the bloodstream, the brain sends signals to
the thyroid glands causing a proliferation of follicular epithelial
cells. With sustained iodine deficiency, the signals
continue to stimulate epithelial cell proliferation and produce thyroid
Thyroid problems are further complicated by certain feeds such as rapeseed, flax, soybean, cabbage, and broccoli which block the normal production of thyroxine. During this prebreeding/breeding season, I feed almost no rape or flax seed and feed peas instead of other vegetables. Providing one drop
of dilute Lugol's solution in 1 oz. of fresh drinking water once a week may be used as a preventative when these foods are being feed.
Canaries with low functioning thyroid hormones are lethargic and seem to lack vigor and when left untreated may contribute to immune deficiency and susceptibility to infection, infertility and embryo death in the shell and decreased hatchability. Even males losing their voice and not singing can be due to iodine deficiency.
Kansas is known for being an area that is iodine deficient. And over the years, I have use Lugol's iodine or vanodine iodine to ensure good thyroid hormone production. Yesterday and today, I added 5 drops vanodine per gallon and today and I can already notice raised activity, and a more "perky" disposition and feeding behavior.
I have a few German rollers from other breeders that were raise primarily on rape seed. One bird was thought to be a hen but actually it was too thin and out of condition male. This bird is now starting to sing after two weeks with two consecutive days each week on vanodine in the water. Likewise the other older Roller male and two hens from another breeder are starting to gain weight. The older male produced very few chicks last year and his son even died and the two hens never came into condition. I think the all rape seed diet had quite a detrimental effect on them.