Thyroid Disease Diagnosis What Is Thyroid Stimulating Hormone? A Message to Your Thyroid Gland to Step up Production By Adrienne Dellwo Adrienne Dellwo LinkedIn Adrienne Dellwo is an experienced journalist who was diagnosed with fibromyalgia and has written extensively on the topic. Learn about our editorial process Updated on August 09, 2022 Medically reviewed by Do-Eun Lee, MD Medically reviewed by Do-Eun Lee, MD LinkedIn Do-Eun Lee, MD, has been practicing medicine for more than 20 years, and specializes in diabetes, thyroid issues and general endocrinology. She currently has a private practice in Lafayette, CA. Learn about our Medical Expert Board Print Table of Contents View All Table of Contents Functions Causes of Abnormal Levels Associated Conditions TSH Test Thyroid-stimulating hormone (TSH) is a hormone that prompts your thyroid gland to produce the thyroid hormones triiodothyronine (T3) and thyroxine (T4). The hypothalamus, located in the brain, constantly monitors your blood for levels of thyroid hormones, and if it detects too little, it triggers the pituitary gland, also located in the brain, to release TSH. This system of communication keeps your thyroid hormone levels within the optimal range. If you have enough or too much T3 or T4, the pituitary gland slows down the production of TSH, which signals your thyroid to produce less T3 and T4. Lars Neumann / iStock / Getty Images Thyroid Hormone Functions The thyroid gland is front and center at the base of your neck, just below your larynx (voice box) and above your sternum. It’s shaped like a butterfly, with two lobes that are joined in the center by a narrow strip of tissue. The hormones made in your thyroid gland are essential to your metabolism, growth, and development. T3 and T4 work together, along with other hormones in your body to regulate many vital functions, including: Metabolic rateWeight loss or gainHeart rateBody temperatureDigestionMuscle controlRespiratory rateBone healthBrain developmentCellular production of energyMenstrual cycleGrowth and development in children Thyroid hormones literally have an impact on every cell in your body, so when their levels are not within normal ranges, that can have a major impact on your health. How Your Thyroid Works Causes of Abnormal TSH Levels Several different things can cause your TSH levels to be abnormal. Some conditions that can affect your thyroid gland include: Primary adrenal insufficiency (Addison's disease) Autoimmune disease that affects the thyroid gland (Hashimoto’s disease, Graves’ disease) Radiation treatments for cancer of or near the thyroid gland Thyroidectomy (removal of all or part of the thyroid gland) Non-functioning thyroid gland at birth Iodine deficiency Taking medication that’s high in iodine Other factors associated with TSH abnormalities include: Aging Pernicious anemia Diabetes type 1 Turner syndrome Iodine is essential for the proper production and function of the thyroid hormones. Your body cannot produce iodine, though, so you have to get it through your diet or nutritional supplements. Some natural sources of iodine are: Fish and other seafood Dairy products Grains Iodized salt Associated Conditions High TSH levels are associated with low levels of thyroid hormones, and low TSH levels are associated with high levels of thyroid hormones. When levels are slightly abnormal and without symptoms, it’s classified as a subclinical thyroid disorder. Some people diagnosed with a subclinical thyroid disorder eventually go on to develop full-blown thyroid disease. A condition called thyroiditis is a type of inflammation of the thyroid gland that interferes with hormone production. It can be associated with either high levels or low levels of TSH. Hyperthyroidism and Graves' disease are associated with low levels of TSH and high thyroid function. Hypothyroidism and Hashimoto's disease are associated with high levels of TSH and low thyroid function. Hyperthyroidism Also called overactive thyroid, this condition accelerates your metabolism. Symptoms include: Unintended weight lossIncreased sweatingRapid heart rateIrregular heart rhythmsHigh blood pressureShortness of breathMalabsorption of nutrientsFrequent urinationInfrequent menstrual periods or no periods at allErectile dysfunctionTremorAnxiety Treating Hyperthyroidism Graves’ Disease In this autoimmune condition, the immune system’s attack on the thyroid gland causes it to malfunction and produce excess hormones. The symptoms are generally the same as those of hyperthyroidism. In addition, Graves’ is often associated with: Goiter (enlarged thyroid gland) Graves’ ophthalmopathy Skin lesions Graves’ ophthalmopathy develops due to the autoimmune process. It can give your eyes a bulging appearance because it causes increased pressure around the eyes. It can also cause eye sensitivity and decreased vision. What Is Graves' Disease? Hypothyroidism Also called underactive thyroid, this condition slows the metabolism and can lead to: Weight gainFatigueLow energy levelsMental fogFrequently being coldHair lossIrregular menstrual cycles and fertility problemsMuscle pain and crampsSlow pulseLow blood pressure Treating Hypothyroidism Hashimoto's Disease Sometimes called Hashimoto's thyroiditis, this is an autoimmune disease in which the immune system attacks healthy thyroid tissues. Symptoms are similar to those of hypothyroidism but may be more severe. Some women experience a drop in thyroid function after giving birth, which is called postpartum thyroiditis. This is typically a temporary condition, with the function returning to normal over time. TSH Testing Interpretations TSH is an important marker for determining whether someone has thyroid disease. TSH Test Result Interpretations mU/L DIAGNOSIS 4.7-10 Subclinical hypothyroidism Over 10 Hypothyroidism 0.1-0.5 Subclinical hyperthyroidism Below 0.1 Hyperthyroidism Sometimes, a healthcare provider will order tests for TSH, free T3, and free T4 together, possibly with other tests to get a more complete picture of how well your thyroid gland is functioning. Understanding Thyroid Test Results A Word From Verywell If you have symptoms that may be suggestive of a thyroid disorder, it's important for you to get an appointment with your healthcare provider. These disorders are common and treatable, so there’s no reason for you to continue dealing with unpleasant—and potentially dangerous—symptoms. Why Do I Have Thyroid Symptoms If My TSH Is Normal? 7 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. University of Michigan: Michigan Medicine. Thyroid hormone production and function. Cleveland Clinic. Thyroid disease. National Institutes of Health, Office of Dietary Supplements. Iodine: Fact sheet for consumers. Sheehan MT. Biochemical testing of the thyroid: TSH is the best and, oftentimes, only test needed - A review for primary care. Clin Med Res. 2016;14(2):83-92. doi:10.3121/cmr.2016.1309 National Institutes of Health, U.S. National Library of Medicine: MedlinePlus. Hyperthyroidism. Bahn RS. Graves' ophthalmopathy. N Engl J Med. 2010;362(8):726–738. doi:10.1056/NEJMra0905750 National Institutes of Health, U.S. National Library of Medicine: MedlinePlus. Hypothyroidism. Updated September 2, 2020. Additional Reading Bahn RA, Burch HB, Cooper DS, Garber JR, Greenlee MC, et al. Hyperthyroidism management guidelines. Endocr Pract. (No.3)457. Garber JR, Cobin RH, Gharib H, Hennessey JV, Klein I, et al. ATA/AACE guidelines for hypothyroidism in adults. Endocr Pract. (No.6)989. National Center for Biotechnology Information, U.S. National Library of Medicine. How does the thyroid gland work? By Adrienne Dellwo Adrienne Dellwo is an experienced journalist who was diagnosed with fibromyalgia and has written extensively on the topic. See Our Editorial Process Meet Our Medical Expert Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Other Helpful Report an Error Submit By clicking “Accept All Cookies”, you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. Cookies Settings Accept All Cookies