Hypothyroidism (underactive thyroid) is a condition in which your thyroid gland doesn't produce enough of certain crucial hormones. Hypothyroidism may not cause noticeable symptoms in the early stages. Over time, untreated hypothyroidism can cause a number of health problems, such as obesity, joint pain, infertility and heart disease.

Symptoms

Hypothyroidism signs and symptoms may include: Fatigue, Increased sensitivity to cold, Constipation, Dry skin, Weight gain, Puffy face, Hoarseness, Muscle weakness, Elevated blood cholesterol level, Muscle aches, tenderness and stiffness, Pain, stiffness or swelling in your joints, Heavier than normal or irregular menstrual periods, Thinning hair, Slowed heart rate, Depression, Impaired memory, Enlarged thyroid gland (goiter).

Causes

When your thyroid doesn't produce enough hormones, the balance of chemical reactions in your body can be upset. There can be a number of causes, including autoimmune disease, hyperthyroidism treatments, radiation therapy, thyroid surgery and certain medications. Your thyroid is a small, butterfly-shaped gland situated at the base of the front of your neck, just below your Adam's apple. Hormones produced by the thyroid gland — triiodothyronine (T3) and thyroxine (T4) — have an enormous impact on your health, affecting all aspects of your metabolism. These hormones also influence the control of vital functions, such as body temperature and heart rate. Hypothyroidism results when the thyroid gland fails to produce enough hormones.