Hashimoto’s thyroiditis is a chronic inflammatory autoimmune thyroid disease in which the immune system attacks and destroys the thyroid gland. The thyroid then produces too little hormone and metabolism is slowed. It is the most common of all the thyroid conditions in the US and women are affected 10 times more often than men. Most diagnoses occur between the ages of 30-50 and prevalence increases with age in both women and men. Symptoms, which often develop gradually, may include weight gain, cold sensitivity, tingling in the hands and feet, fatigue, hair loss, dry hair, fertility problems, and difficulty concentrating. Thyroid hormone should be monitored in women who plan pregnancy. Low thyroid function can affect the development of the baby. Post-partum thyroiditis can develop in the 12 months following childbirth. Women who are having trouble conceiving should also have their thyroid levels checked as thyroid hormone levels can affect ovulation.