{"id":18312,"date":"2026-09-24T00:13:08","date_gmt":"2026-09-23T22:13:08","guid":{"rendered":"https:\/\/www.badania-medyczne.pl\/hypothyroidism-symptoms-causes-and-blood-tests\/"},"modified":"2026-09-24T00:13:08","modified_gmt":"2026-09-23T22:13:08","slug":"hypothyroidism-symptoms-causes-and-blood-tests","status":"publish","type":"post","link":"https:\/\/www.badania-medyczne.pl\/en\/hypothyroidism-symptoms-causes-and-blood-tests\/","title":{"rendered":"Hypothyroidism: Symptoms, Causes and Which Tests to Have"},"content":{"rendered":"<p>Hypothyroidism (an underactive thyroid) is one of the most common endocrine disorders. It affects several per cent of adults, with women five to eight times more likely to develop it than men. Mild, subclinical forms are even more common. Hypothyroidism is also easy to overlook because its symptoms are non-specific: fatigue, weight gain, feeling cold, dry skin and low mood. Many people attribute these symptoms to stress or ageing for years. Yet diagnosis begins with a simple, inexpensive blood test, and treatment is effective and generally well tolerated.<\/p>\n<h2>What does the thyroid do, and what happens when it becomes underactive?<\/h2>\n<p>The thyroid gland produces thyroxine (T4) and triiodothyronine (T3), hormones that regulate metabolism in virtually every cell of the body. Their production is controlled by the pituitary gland through thyroid-stimulating hormone (TSH). When thyroid hormone levels are too low, the pituitary gland releases more TSH to stimulate the thyroid. This is why TSH rises in hypothyroidism, while FT4 (free thyroxine) falls or, in the early stages, remains within the reference range. Metabolism slows down: the heart beats more slowly, bowel movements become less frequent, the skin and hair become dry, the body retains fluid and cholesterol levels rise.<\/p>\n<h2>Most common causes<\/h2>\n<ul>\n<li><strong>Hashimoto&#8217;s thyroiditis<\/strong> (chronic autoimmune thyroiditis): the most common cause in Poland. The immune system gradually damages the thyroid gland. Anti-TPO and anti-TG antibodies are markers of the condition.<\/li>\n<li><strong>Previous treatment for hyperthyroidism<\/strong> with radioactive iodine or thyroid surgery.<\/li>\n<li><strong>Medicines:<\/strong> amiodarone, lithium, interferon and certain cancer treatments.<\/li>\n<li><strong>Iodine deficiency or excess<\/strong>, and, less commonly, congenital thyroid disorders and pituitary disease (central hypothyroidism, which may be associated with low TSH).<\/li>\n<li><strong>Postpartum period:<\/strong> temporary postpartum thyroiditis, which can develop into permanent hypothyroidism in some women.<\/li>\n<\/ul>\n<h2>Symptoms that should prompt thyroid testing<\/h2>\n<p>No single symptom is exclusive to hypothyroidism. Several of the following symptoms usually occur together and develop gradually:<\/p>\n<ul>\n<li>persistent fatigue, sleepiness, sluggishness and difficulty concentrating,<\/li>\n<li>weight gain despite an unchanged diet, swelling (particularly of the face and eyelids),<\/li>\n<li>feeling cold, cold hands and feet,<\/li>\n<li>dry, pale skin, brittle hair and nails, hair loss and thinning eyebrows,<\/li>\n<li>constipation,<\/li>\n<li>low mood, apathy and sometimes depression-like symptoms,<\/li>\n<li>in women: heavy or irregular periods, difficulty conceiving and miscarriage,<\/li>\n<li>a slow heart rate, raised cholesterol, a hoarse voice, and muscle and joint pain.<\/li>\n<\/ul>\n<h2>Tests: where to start<\/h2>\n<h3>TSH<\/h3>\n<p>Thyroid-stimulating hormone (TSH) &#8211; laboratory test is the first-line investigation. A normal TSH level in someone without symptoms virtually excludes primary hypothyroidism. The reference range in most laboratories is approximately 0.3\u20134.2 mIU\/l, although it depends on the testing method, age and pregnancy (lower reference values apply during the first trimester). An elevated TSH result should be followed by an FT4 test.<\/p>\n<h3>FT4 and FT3<\/h3>\n<p>Elevated TSH together with low FT4 indicates overt hypothyroidism. Elevated TSH with normal FT4 indicates subclinical hypothyroidism, which does not always require treatment but does require monitoring. Free triiodothyronine (FT3) &#8211; laboratory test is less important in diagnosing hypothyroidism; it is mainly used when investigating hyperthyroidism and in certain specific circumstances.<\/p>\n<h3>Anti-TPO and anti-TG<\/h3>\n<p>Antibodies against thyroid peroxidase (anti-TPO) and thyroglobulin (anti-TG) help confirm an autoimmune cause, namely Hashimoto&#8217;s thyroiditis. High antibody levels in someone whose TSH is still normal indicate an increased risk of developing hypothyroidism in subsequent years and justify annual TSH monitoring.<\/p>\n<h3>Thyroid ultrasound<\/h3>\n<p>Although not a blood test, thyroid ultrasound provides additional diagnostic information. In Hashimoto&#8217;s thyroiditis, the gland typically has a heterogeneous, hypoechoic appearance. Ultrasound can also detect thyroid nodules that require further assessment.<\/p>\n<h3>Additional tests<\/h3>\n<p>Lipid profile (cholesterol) &#8211; laboratory test (hypothyroidism raises LDL cholesterol), full blood count and Ferritin &#8211; laboratory test (Hashimoto&#8217;s thyroiditis often coexists with anaemia and iron deficiency, while iron deficiency can impair thyroid hormone function), Vitamin B12 &#8211; laboratory test (autoimmune gastritis may coexist with Hashimoto&#8217;s thyroiditis), 25-hydroxyvitamin D (25 OH) &#8211; vitamin D test and Glucose &#8211; laboratory test. TSH testing is essential for women planning pregnancy because untreated hypothyroidism increases the risk of miscarriage and can affect the baby&#8217;s development.<\/p>\n<h2>Interpreting results: what common patterns mean<\/h2>\n<table>\n<thead>\n<tr>\n<th>TSH<\/th>\n<th>FT4<\/th>\n<th>Most likely interpretation<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>normal<\/td>\n<td>normal<\/td>\n<td>normal thyroid function<\/td>\n<\/tr>\n<tr>\n<td>elevated<\/td>\n<td>normal<\/td>\n<td>subclinical hypothyroidism: monitoring, repeat testing after 6\u201312 weeks; the decision to treat depends on TSH level, symptoms, antibodies and pregnancy<\/td>\n<\/tr>\n<tr>\n<td>elevated<\/td>\n<td>low<\/td>\n<td>overt primary hypothyroidism: levothyroxine treatment is indicated<\/td>\n<\/tr>\n<tr>\n<td>low or normal<\/td>\n<td>low<\/td>\n<td>suspected central (pituitary-related) hypothyroidism: endocrinological assessment required<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>A single, mildly elevated TSH result should be repeated after a few weeks because TSH may rise temporarily following an infection, with insufficient sleep, during recovery from illness or as a result of certain medicines. Reference ranges and treatment decisions should be assessed by a doctor. The table is intended only to help you understand which questions to ask during your appointment.<\/p>\n<h2>Treatment and monitoring<\/h2>\n<p>Standard treatment is levothyroxine, a synthetic form of T4, taken in the morning on an empty stomach, 30\u201360 minutes before breakfast, with appropriate intervals between doses and iron supplements, calcium supplements and proton pump inhibitors. The dose is adjusted gradually, with TSH checked 6\u20138 weeks after each change. Once TSH has stabilised, monitoring is usually performed every 6\u201312 months. Symptoms generally improve within a few weeks. Weight loss is usually modest and mainly reflects the loss of retained fluid, so levothyroxine is not a weight-loss medicine.<\/p>\n<h2>Preparing for thyroid blood tests<\/h2>\n<p>Blood samples are best collected in the morning, between 7:00 and 10:00, because TSH follows a circadian rhythm. People taking levothyroxine should take their tablet after blood collection. High doses of biotin (found in hair and nail supplements) can interfere with thyroid hormone test results and should be stopped 2\u20133 days before testing. Fasting is not strictly necessary for TSH testing alone, but if a lipid profile or glucose test is also being performed, you should avoid food for 12 hours.<\/p>\n<div class=\"bm-cta\" style=\"margin:28px 0;padding:22px 24px;border-left:5px solid #e63946;background:#f6f8fb;border-radius:6px\">\n<p style=\"margin:0 0 10px;font-size:1.15em\"><strong>Think you may have a thyroid problem? Check your TSH and FT4 without a referral (a formal request for testing from a doctor), then take your results to your doctor:<\/strong><\/p>\n<ul style=\"margin:0 0 12px 18px\">\n<li><a href=\"https:\/\/badamysie.pl\/produkt\/pakiet-tarczycowy-2\/?utm_source=badania-medyczne&#038;utm_medium=artykul\" target=\"_blank\" rel=\"noopener\">Thyroid test panel (FT4, TSH)<\/a> \u2013 TSH, FT4<\/li>\n<li><a href=\"https:\/\/badamysie.pl\/produkt\/pakiet-tarczycowy-rozszerzony-2\/?utm_source=badania-medyczne&#038;utm_medium=artykul\" target=\"_blank\" rel=\"noopener\">Thyroid test panel+ (TSH, FT4, FT3, anti-TPO, anti-TG)<\/a> \u2013 including FT3 and thyroid antibodies<\/li>\n<li><a href=\"https:\/\/badamysie.pl\/produkt\/pakiet-anemia-2\/?utm_source=badania-medyczne&#038;utm_medium=artykul\" target=\"_blank\" rel=\"noopener\">Anaemia test package<\/a> \u2013 full blood count, ESR, Iron &#8211; laboratory test, Ferritin &#8211; laboratory test, Vitamin B12 &#8211; laboratory test<\/li>\n<\/ul>\n<p style=\"margin:0\">Buy online at <a href=\"https:\/\/badamysie.pl\/?utm_source=badania-medyczne&#038;utm_medium=artykul\" target=\"_blank\" rel=\"noopener\">BadamySie.pl<\/a>, with blood collection available without a referral at one of over 800 ALAB, Synevo and ETER-MED collection centres across Poland, and results available online. Find collection centre addresses: <a href=\"https:\/\/www.badania-medyczne.pl\/en\/category\/blood-collection-centres\/\">blood tests near you<\/a>.<\/p>\n<\/div>\n<h2>Frequently asked questions<\/h2>\n<h3>Can hypothyroidism be cured?<\/h3>\n<p>Hashimoto&#8217;s thyroiditis usually requires lifelong thyroid hormone replacement, but with the correct dose, people can lead normal lives. Temporary forms, such as postpartum or drug-induced hypothyroidism, may resolve.<\/p>\n<h3>How often should I check TSH if I have positive anti-TPO antibodies but normal TSH?<\/h3>\n<p>Usually once a year, and always before a planned pregnancy and during early pregnancy.<\/p>\n<h3>Is a TSH result alone sufficient for diagnosis?<\/h3>\n<p>For initial screening, yes. A complete diagnosis and treatment decision require FT4 testing, usually antibody testing, and a clinical assessment by a doctor.<\/p>\n<h2>Sources<\/h2>\n<ul class=\"bm-sources\">\n<li>NICE, Thyroid disease: assessment and management (NG145), 2019, updated 2023. <a href=\"https:\/\/www.nice.org.uk\/guidance\/ng145\" rel=\"noopener\" target=\"_blank\">nice.org.uk<\/a><\/li>\n<li>Jonklaas J. et al., American Thyroid Association, Thyroid, Guidelines for the Treatment of Hypothyroidism, 2014. <a href=\"https:\/\/journals.sagepub.com\/doi\/10.1089\/thy.2014.0028\" rel=\"noopener\" target=\"_blank\">journals.sagepub.com<\/a><\/li>\n<li>Pearce SHS et al., European Thyroid Association, 2013 ETA Guideline: Management of Subclinical Hypothyroidism, 2013. <a href=\"https:\/\/karger.com\/etj\/article\/2\/4\/215\/150009\/2013-ETA-Guideline-Management-of-Subclinical\" rel=\"noopener\" target=\"_blank\">karger.com<\/a><\/li>\n<li>AOTMiT (Polish Agency for Health Technology Assessment and Tariff System), Prevention of Thyroid Diseases: Report on Recommended Medical Technologies, 2022. <a href=\"https:\/\/www.aotm.gov.pl\/wp-content\/uploads\/2024\/05\/Raport-AOTMiT.pdf\" rel=\"noopener\" target=\"_blank\">aotm.gov.pl<\/a><\/li>\n<\/ul>\n<div class=\"bm-review\" style=\"margin:28px 0 8px;padding:14px 18px;border-left:4px solid #0b2a4a;background:#f4f7fa;font-size:14px;line-height:1.55\"><strong>Medical review:<\/strong> Dr Tomasz Niew\u0119g\u0142owski, MD, PhD, specialist in internal medicine and sports medicine (PWZ 4049405, Polish medical licence number). Article prepared by the <a href=\"https:\/\/www.badania-medyczne.pl\/en\/editorial-team-and-editorial-standards\/\">Badania-Medyczne.pl Editorial Team<\/a>; AI tools were used for language editing. This content is for informational purposes only and does not replace medical advice. <strong>Date of last review:<\/strong> 1.10.2026.<\/div>\n<div class=\"bm-related\" style=\"margin:28px 0 0;padding:18px 22px;background:#fff;border:1px solid #e3e9f0;border-radius:12px\">\n<p style=\"margin:0 0 8px;font-weight:700;color:#0b2a4a\">Related articles<\/p>\n<ul style=\"margin:0 0 0 18px\">\n<li><a href=\"https:\/\/www.badania-medyczne.pl\/en\/prediabetes-how-to-detect-it-early\/\">Prediabetes: how to detect it before it develops into diabetes<\/a><\/li>\n<li><a href=\"https:\/\/www.badania-medyczne.pl\/jak-wzmocnic-odpornosc-u-dzieci\/\">How to strengthen children&#8217;s immune systems<\/a><\/li>\n<li><a href=\"https:\/\/www.badania-medyczne.pl\/dziecko-poszlo-przedszkola-zobacz-jakich-chorob-mozesz-spodziewac\/\">Has your child started nursery? Find out which illnesses to expect!<\/a><\/li>\n<\/ul>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Hypothyroidism: symptoms, causes (including Hashimoto&#8217;s thyroiditis), and blood tests such as TSH, FT4 and anti-TPO. Learn how to interpret thyroid test results, understand levothyroxine treatment and prepare for testing.<\/p>\n","protected":false},"author":12,"featured_media":16530,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3742],"tags":[],"class_list":["post-18312","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-diseases"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.5 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Hypothyroidism: Tests | Badania-Medyczne.pl<\/title>\n<meta name=\"description\" content=\"Hypothyroidism symptoms, Hashimoto&#039;s thyroiditis, TSH, FT4 and anti-TPO tests, result interpretation, treatment and preparation. 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