Goiter is a condition in which the thyroid gland becomes enlarged. It is usually caused by a lack of iodine in the diet, and can lead to symptoms such as a swelling in the throat, difficulty swallowing, hoarseness, and coughing. Treatment for goiter typically involves supplementing the diet with iodine, and in more severe cases, surgery may be necessary.

Hypothyroidism is a condition in which the thyroid gland does not produce enough of the hormones thyroxine (T4) and triiodothyronine (T3). This can lead to symptoms such as fatigue, weight gain, depression, and constipation. Treatment typically involves taking thyroid hormone replacement medication.

Hyperthyroidism is a condition in which the thyroid gland produces too much of the hormones thyroxine (T4) and triiodothyronine (T3). This can lead to symptoms such as weight loss, hair loss, rapid heart rate, anxiety, and insomnia. Treatment typically involves taking medications to reduce thyroid hormone levels, and in more severe cases, radioactive iodine treatment or surgery may be necessary.