Hypothyroidism is an endocrine disorder in which your thyroid gland is underactive. This is a problem because your thyroid gland is responsible for producing other hormones that help regulate some of your body's functions. Hypothyroidism is easily diagnosed with a routine blood test. It is also easily treated by using thyroid hormone medication.
Symptoms of hypothyroidism include lack of energy, sensitivity to cold, depression, weight gain, muscle aches and weakness, dry skin, heavy menstual periods, and constipation. Depending on the degree of hypothyroidism you have, these symptoms can be quite severe.