In addition to hyperthyroidism, there are a handful of related thyroid disorders that affect the structure or function of the thyroid gland. These include hypothyroidism, goiter, thyroid nodules, and thyroid cancer. The main difference between hyperthyroidism and hypothyroidism is that ‘hyper’ refers to an overactive thyroid, or the presence of too much thyroid hormone in the system, while ‘hypo’ means an underactive thyroid, or too little thyroid hormone is present in the body. As for goiter, thyroid nodules, and thyroid cancer, each of these involve structural or functional abnormalities of the thyroid, which are discussed in greater detail below.
Hypothyroidism refers to a condition in which the thyroid gland produces an insufficient amount of thyroid hormone. This is often due to problems within the thyroid gland, the pituitary gland, or the hypothalamus. Common causes of hypothyroidism include thyroid hormone resistance, Hashimoto’s thyroiditis, and other types of thyroiditis, such as acute thyroiditis and postpartum thyroiditis. The term thyroiditis simply means inflammation of the thyroid and encompasses a multitude of disorders, all of which cause thyroidal inflammation but present themselves in different ways. Hashimoto’s thyroiditis is by far the most common cause of hypothyroidism, an autoimmune condition named after Japanese physician Hakaru Hashimoto. Symptoms of hypothyroidism include fatigue and depression, poor concentration and muscle aches, dry skin and fluid retention, as well as feeling cold and excessive menstrual bleeding in women.
Goiter describes a condition in which the thyroid gland becomes enlarged and causes the neck to swell. It is one of the most common types of thyroid disorders and is most often caused by iodine deficiency in the diet. The majority of goiters are harmless and do not require treatment, but if it becomes large enough in size or causes one or more symptoms to occur, active treatment may be necessary. Depending on the size, symptoms may include swelling or tightness in the neck, difficulty breathing or swallowing, involuntary coughing or wheezing, and hoarseness of the voice. Goiters may be associated with hyperthyroidism, hypothyroidism, or euthyroidism, the latter of which is defined as normal thyroid function.
Thyroid nodules are solid lumps or fluid-filled growths that form on or in the thyroid gland. Generally speaking, these abnormal masses are caused by benign cysts, benign tumors, or cancers of the thyroid. Approximately 1 percent of men and 5 percent of women who live in iodine-sufficient countries have thyroid nodules that are large enough to feel, while about 50 percent have nodules that are too small to feel. In addition to variations in size, the nodules can be single or multiple, as well as benign or cancerous. Most thyroid nodules don’t cause any symptoms, although when they do, the symptoms are very similar to those of hyperthyroidism.
Thyroid cancer comes in many different forms, depending on which cell type within the thyroid has become cancerous. This disease is far more common in adult women than it is in adult men and in youth. That said, thyroid cancer is the most common type of endocrine cancer in children, the symptoms of which include swollen glands, a lump or tight feeling in the neck, trouble breathing or swallowing, and a hoarse voice. Thankfully, the prognosis is generally good and the survival rate is fairly high, especially when diagnosed early.