An Overview of Hypothyroidism By Mary Shomon | Reviewed by a board-certified physician Updated April 18, 2018 Print Hypothyroidism is a condition in which your thyroid gland—a small, butterfly-shaped gland in your neck—does not produce enough thyroid hormone. It is sometimes referred to as an "underactive" thyroid. Hypothyroidism slows down a person's metabolism, leading to symptoms like weight gain, sluggishness, feeling cold, and more. A simple blood test called thyroid-stimulating hormone (TSH) can diagnose hypothyroidism, and thyroid hormone replacement medication can treat it. By gaining knowledge about hypothyroidism, including what it feels like to have this thyroid problem, and how it's diagnosed and managed, you will be more prepared and self-assured as you embark on your thyroid journey.A look at the anatomy of the thyroid, located above the collarbone.SymptomsYour thyroid gland uses dietary iodine to make thyroid hormone. When there is a deficiency in thyroid hormone, your body has trouble using energy and staying warm. Article Treating Subclinical Hypothyroidism in Pregnancy Article Hypothyroidism and Migraines: Understanding the Link Your muscles, brain, and other organs may also have trouble functioning.The signs and symptoms of hypothyroidism are variable and can be subtle, even mistaken for stress or another medical problem.Here is a closer look at some of the symptoms a person with an underactive thyroid may experience:Feeling fatigued and exhausted, even after a lengthy sleepFeeling depressed or blueGaining weight, despite no change to your healthy diet and exerciseExperiencing “brain fog” and difficulty concentratingFeeling feel cold when others feel hotNoticing hair that is coarse and dry, breaking, brittle, or falling out Noticing skin that is coarse, dry, scaly, and thick, especially the soles of your feetAn unusually low pulse or blood pressureSlow or sluggish reflexesPuffiness in the face, especially around the eyesHigh cholesterol levels that are unresponsive to cholesterol-lowering medicationIrregular menstrual cyclesExperiencing muscle crampsCausesThere are a number of health issues and conditions that cause hypothyroidism.The autoimmune disease Hashimoto’s thyroiditis is the most common cause of hypothyroidism in the United States. In this disease, antibodies attack the thyroid gland, making it incapable of functioning properly.Post-surgical hypothyroidism refers to insufficient thyroid hormone due to surgical removal of all or part of the thyroid gland. Surgery on the thyroid is known as a thyroidectomy.Radiation-induced hypothyroidism may occur from radioactive iodine (RAI) therapy, which is used to treat hyperthyroidism and thyroid cancer. Exposure to radiation treatments to the head and neck, or radioactive fallout from nuclear accidents like Chernobyl or Fukushima, may also cause hypothyroidism. Article Liquid Levothyroxine Better for Hypothyroid Patients Article Thyroid Replacement Therapy for Hypothyroidism With congenital hypothyroidism, newborns come into the world without a thyroid gland or with a partial thyroid gland.Hypothyroidism may also result from taking certain medications (called drug-induced hypothyroidism). While this is not a comprehensive list, some of the more commonly known medications include:LithiumAmiodaroneInterferon alphaInterleukin-2Hypothyroidism can occur with too little iodine consumption (called iodine-deficiency hypothyroidism) or if too much iodine is consumed (called iodine-induced hypothyroidism).In secondary or central hypothyroidism, the pituitary gland (located in your brain) is damaged (from a tumor, radiation, or surgery) and is unable to trigger your thyroid gland to produce thyroid hormone.Rarely, hypothyroidism from infiltrative diseases (for example, sarcoidosis or hemochromatosis) can deposit substances (like granulomas or iron, respectively) into the thyroid gland, reducing its ability to function.DiagnosisThe diagnosis of hypothyroidism requires a clinical examination and blood tests. Clinical Examination In addition to a clinical thyroid examination, which includes a manual and visual examination of the thyroid gland, a doctor will also perform a physical examination to look for signs of hypothyroidism. Some of these signs include dry, coarse skin, a slow heart rate, slow reflexes, and swelling.Blood TestsThe main blood test used to diagnose hypothyroidism is the thyroid stimulating hormone (TSH) test. This test measures TSH, a pituitary hormone. TSH rises when it detects low levels of thyroid hormone, and drops when it detects excess thyroid hormone. Laboratories have established a reference range, and levels above the reference range are considered potentially indicative of hypothyroidism.In addition, the unbound and available levels of the actual circulating thyroid hormones—free thyroxine (free T4) and free triiodothyronine (free T3)—may be measured. There are reference ranges for these two hormone tests, and levels below the reference range (showing that there is insufficient free T4 and/or free T3) are considered indicative of hypothyroidism. Article Is Your TSH Normal, But You Still Have Symptoms? Article Is Your Hypothyroidism Being Undertreated? TreatmentHypothyroidism is treated with a thyroid hormone replacement drug, which is a medication that replaces the missing thyroid hormone in the body.LevothyroxineThe most commonly prescribed thyroid hormone replacement drug is known generically as levothyroxine, a synthetic form of the thyroid hormone thyroxine (T4).LiothyronineThere is also a synthetic form of the T3 hormone, known as liothyronine. It is sometimes added to levothyroxine as part of a therapy known as T4/T3 combination treatment, though this practice is considered controversial by the many endocrinologists and mainstream practitioners.Natural Desiccated ThyroidFinally, there is a hormone replacement drug called natural desiccated thyroid, sometimes abbreviated NDT or called "thyroid extract." NDT contains natural forms of both T4 and T3. While it has been available for more than a century, and is still in use today, it is considered controversial by the mainstream medical community and is prescribed more often by integrative, functional, and holistic physicians, as compared to endocrinologists and conventional physicians.The official guidelines of various endocrinology organizations position levothyroxine as the preferred treatment, and discourage both T4/T3 combination therapy and use of NDT.A Word From VerywellWhether you (or a loved one) has been recently diagnosed with hypothyroidism, or you are being currently treated for it, but still not feeling right, please know that you are not alone. Continue to seek knowledge about your thyroid disease and remain resilient as you navigate this sometimes taxing journey.Also, remember that living well with hypothyroidism is not just about medication. It's also important to eat well, get enough rest, make time for exercise and play, and manage your stress. And even if you feel like you’re fighting an uphill battle with doctors, treatments, and debilitating symptoms, don't give up. You will eventually find the answers that will help you live well and feel well.Sources:American Thyroid Association. (n.d.). Hypothyroidism (Underactive). Braverman, L, Cooper D. Werner & Ingbar's The Thyroid, 10th Edition. WLL/Wolters Kluwer; 2012.Garber J et. al. Clinical Practice Guidelines for Hypothyroidism in Adults: Cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012 Nov-Dec;18(6):988-1028.