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Sources
University of Navarra Clinic (2024). “Hypothyroidism: symptoms, diagnosis and treatment.” — Epidemiology, Hashimoto, TSH diagnosis.
MSD Manual (2024). “Hypothyroidism: Symptoms, Causes, and Management with Levothyroxine.”
Merck Manuals (2024). “Hyperthyroidism: Symptoms, Diagnosis, and Treatment.”
PubMed/Medicine (2025). “Clinical efficacy of selenium supplementation in patients with Hashimoto thyroiditis: systematic review and meta-analysis.” 21 studies, 1,610 patients.
Viamed Health (2026). “Hypothyroidism: symptoms, causes and medical treatment.” — Normal TSH ranges, causes and medication.
Frequently Asked Questions About the Thyroid: Symptoms of Hypothyroidism and Remedies
What are the most common symptoms of an underactive thyroid (hypothyroidism)?
The most common symptoms of hypothyroidism are: extreme fatigue that doesn’t improve with sleep, weight gain without dietary changes, noticeable hair loss, feeling constantly cold when others are comfortable, dry skin, constipation, unexplained depression, and difficulty concentrating. If you have three or more of these symptoms, ask your doctor for a TSH blood test.
How is hypothyroidism diagnosed?
A blood test that measures TSH (thyroid-stimulating hormone) is the most sensitive method and can detect hypothyroidism even before symptoms become severe. The normal TSH range in adults is 0.4 to 4.5 mIU/L. If your TSH is above this value, it indicates that the thyroid gland is not producing enough hormone. In some cases, this test is supplemented with free T4 and TPO antibodies to detect Hashimoto’s thyroiditis.
Does selenium help with hypothyroidism and Hashimoto’s?
Yes, with solid scientific evidence. A meta-analysis published in 2025 that analyzed 21 controlled clinical trials with 1,610 patients with Hashimoto’s thyroiditis demonstrated that selenium supplementation significantly reduces TPOAb antibodies at 3 months and TgAb antibodies at 3 months of treatment. The dose studied was 200 mcg/day. Brazil nuts (2-3 per day) are the most concentrated and accessible food source.
What is the difference between hypothyroidism and hyperthyroidism?
In hypothyroidism, the thyroid gland produces too little hormone, causing the body to slow down: fatigue, feeling cold, weight gain, and depression. In hyperthyroidism, the thyroid gland produces too much hormone, causing the body to speed up: anxiety, tremors, palpitations, rapid weight loss, and heat intolerance. Both are diagnosed with a TSH test: high TSH = hypothyroidism; low TSH = hyperthyroidism. Eighty percent of thyroid problems are hypothyroidism.