What is the medical term for an underactive thyroid?

The medical term for an underactive thyroid is hypothyroidism. This condition occurs when the thyroid gland produces insufficient amounts of thyroid hormones, which are crucial for regulating metabolism, energy levels, and overall bodily functions.

In hypothyroidism, symptoms can include fatigue, weight gain, cold intolerance, dry skin, and depression, among others. The diagnosis is often confirmed through blood tests that measure levels of thyroid-stimulating hormone (TSH) and thyroid hormones like thyroxine (T4).

The other terms provided describe different aspects related to thyroid function. Hyperthyroidism refers to an overactive thyroid that produces excessive hormones, leading to symptoms such as weight loss, rapid heartbeat, and anxiety. Thyroiditis is the inflammation of the thyroid gland, which can sometimes lead to hormone imbalances. Goiter refers to an enlargement of the thyroid gland, which can occur in both hypothyroidism and hyperthyroidism but is not synonymous with either condition.