Symptoms of an underactive thyroid, or hypothyroidism, include unexpected weight gain, dry skin, constipation, higher cold sensitivity, changes in the menstrual cycle and fatigue, according to Mayo Clinic. People with hypothyroidism may also experience increased blood cholesterol level, muscle weakness, hoarseness, depression, slow heart rate, dry hair or hair loss and a swollen face.
Those with hypothyroidism experience varying symptoms, depending on how deficient they are in thyroid hormones, notes Mayo Clinic. Most people develop symptoms gradually over several years. Symptoms such as weight gain and fatigue are typically not noticeable in the initial stages. However, they start to manifest as the body's metabolism becomes slower.
Untreated hypothyroidism can lead to serious symptoms and other health problems, such as heart disease, infertility, joint pain or obesity, says Mayo Clinic. The thyroid may also become enlarged due to continuous stimulation of the thyroid gland to produce more hormones. Patients with hypothyroidism may also suffer forgetfulness, slower thought processes or depression.
Many of the symptoms associated with an underactive thyroid may mimic other conditions or be vague in nature, states WebMD. Some groups of people are at a higher risk for developing hypothyroidism such as people with autoimmune disorders, bipolar disorder or Down syndrome. Women above 60 years old are prone to developing hypothyroidism, states Mayo Clinic.
A rare type of hypothyroidism, called myxedema, is a life-threatening condition that causes unresponsiveness, lower body temperature, difficulty in breathing, lower blood pressure or coma. Anyone who feels unexplained tiredness or experiences any of the symptoms of hypothyroidism should consult a doctor. Individuals who undergo treatment methods such as thyroid surgery, radioactive iodine treatment or anti-thyroid medications require periodic testing of the thyroid function.