Which condition is characterized by an underactive thyroid gland?

The condition characterized by an underactive thyroid gland is hypothyroidism. This occurs when the thyroid gland does not produce sufficient amounts of thyroid hormones, which are crucial for regulating metabolism, energy levels, and overall bodily functions. As a result, individuals with hypothyroidism may experience symptoms such as fatigue, weight gain, cold intolerance, and depression, among others.

Hypothyroidism can be caused by various factors, including autoimmune diseases, certain medications, or damage to the thyroid gland from radiation or surgery. One specific autoimmune condition that can lead to hypothyroidism is Hashimoto's thyroiditis, which involves the immune system attacking the thyroid gland. However, while Hashimoto's thyroiditis is a cause of hypothyroidism, the term itself specifically refers to the underactive state of the thyroid gland and not the condition causing it.

Goiter refers to the enlargement of the thyroid gland and can be associated with both hypothyroidism and hyperthyroidism, rather than being indicative of an underactive gland on its own. Overall, hypothyroidism is the most direct and accurate term for describing the state of an underactive thyroid gland.