What are the most common types of thyroid problems?

Common types of thyroid problems include an underactive thyroid or an overactive thyroid. Common signs of underactive thyroid include hair loss, weight gain, fatigue, constipation and cold intolerance. Overactive thyroid signs include heart palpitations, heat intolerance, diarrhea, hot flashes, weight loss and fatigue.

Most thyroid conditions are benign or noncancerous. They include benign cysts, nodules, adenomas, or goiters (swelling or enlargement) on the thyroid gland, which is in the neck. Often doctors can detect these problems during a physical exam.

Your thyroid secretes thyroid hormone, which helps to regulate your metabolism. If your thyroid is underactive (hypothyroidism), it does not produce enough hormone. You may experience fatigue, weight gain, forgetfulness, feeling cold, constipation, depression and, in women, excessive menstrual bleeding.
If your thyroid is overactive (hyperthyroidism), it produces too much hormone. You may experience symptoms including feeling hot, nervous and jittery, sweating excessively, increased bowel movements, rapid heart rate, weight loss, decreased concentration, fatigue and, in women, scant or irregular menstrual flow.
Some thyroid conditions are related to problems with the immune system. In Hashimoto's disease, the immune system attacks the thyroid and slowly destroys it. In Graves' disease, the immune system acts on the thyroid gland, causing it to produce too much thyroid hormone, leading to hyperthyroidism. Graves' disease may also cause the well-known bulging eye appearance that many people associate with thyroid problems.