ASK THE VET (Thyroid Enlargement)

Birds, unlike mammals, have two separate paired thyroid glands. These are located at the thoracic inlet. Normal thyroid glands are not palpable (able to be felt with one's fingers) because of their location in the anterior thoracic cavity. Thyroid glands secrete a hormone known as thyroxine which controls the metabolic rate of the body. Enlargement of the thyroid glands is known as goiter. The most common cause of goiter in birds (and other animals) is iodine deficiency, either due to a lack of iodine in the diet or to a substance that induces goiter (certain plants). Birds on an all seed diet are at risk of developing an iodine deficiency. Excessive intake of iodine as well as thyroid neoplasia, have also been found to result in goiter. Goiter has been diagnosed in poultry, budgerigars, canaries, pigeons, and other species of birds.

Enlarged thyroid glands can sometimes be palpitated or seen in a radiograph in the thoracic inlet. Clinical signs of thyroid enlargement are the result of pressure on the syrinx (voice box) and lower trachea. The enlarged glands cause obstruction of the movement of air in the respiratory tract, resulting in expiratory dyspnea.

In budgerigars, dyspnea, regurgitation, a mucus-filled crop, a loss of voice, and a hiss pitched respiratory squeak may occur.

In pigeons, goiter may lead to hypothyroidism. Lethargy, obesity, poor feathering and reproductive problems such as decreased fertility, decreased hatching rates and unhealthy squabs may occur.

Therapeutic measures for goiter can be initiated if the condition is recognized early in the course of the disease. If the bird is eating and drinking, Lugol's Iodine Solution can be added to the drinking water. Alternatively, cod liver oil, which is very high in iodine can be added to the food. If the bird is unable to eat or drink, injection of NaI (Sodium Iodide) can be given intramuscularly. The bird should be placed on a complete formulated diet.