Hypothyroidism/Myxedema is a disease characterized by a decrease in the basal metabolic rate due to hyposecretion of T3 and T4 hormones from the thyroid gland. It most commonly occurs in people over 50 years of age but can affect people of any age, and is 5 times more prevalent in females than males. Symptoms include fatigue, weight gain, dry skin, puffy face, cold intolerance, and menstrual disturbances. Diagnosis involves testing thyroid function and hormone levels, while treatment consists of lifelong thyroid hormone replacement therapy with levothyroxine.