Quick answer: TSH (thyroid-stimulating hormone) is made by the pituitary gland and tells the thyroid how much hormone to make. It is usually the first thyroid test. High TSH typically means the thyroid is underactive (hypothyroidism); low TSH typically means it is overactive (hyperthyroidism). TSH is best read with free T4 and, when needed, free T3 and thyroid antibodies.
What is TSH?
TSH is a pituitary hormone. When thyroid hormone is low, TSH rises to push the thyroid harder; when thyroid hormone is high, TSH falls. This marker is part of the Healthspan Assessment panel available to my 1-on-1 patients.
Why TSH matters
- Screens for thyroid disease
- Monitors thyroid medication
- Reflects the brain-thyroid feedback loop
Understanding your result
Reference ranges vary by lab, age and sex. Your provider interprets your result against the lab’s range and your overall picture, rather than chasing a single number. Functional labs are optional. They can be helpful in more complex cases, and in my practice they are available only to patients working 1-on-1 with me.
What low TSH can mean
- Hyperthyroidism, including Graves’ disease
- Too much thyroid medication
- Rarely, pituitary problems
What high TSH can mean
- Hypothyroidism, including Hashimoto’s
- Recovery from illness
- Not enough thyroid medication
- Iodine deficiency
What affects TSH
- Time of day (higher at night and early morning)
- Illness and stress
- Biotin supplements
- Age and pregnancy
Ways to support healthy levels
- Eat enough protein and calories; very low-calorie dieting can slow thyroid hormone activation
- Get iodine from food such as seafood, dairy and iodized salt, but avoid high-dose iodine supplements unless prescribed
- Selenium (Brazil nuts, seafood), zinc and iron support thyroid hormone production and conversion
- Manage stress and sleep
- Take thyroid medication as prescribed and retest as your doctor advises
TSH and healthy aging
Thyroid hormones set the pace of metabolism in nearly every cell and directly influence mitochondria, the energy factories of the cell. Thyroid function and autoimmunity both change with age, so keeping an eye on thyroid health supports energy, heart health and healthy weight over time.
Related thyroid tests: free T4, free T3, reverse T3, TPO antibodies, thyroglobulin antibodies.
When to see a naturopathic doctor
- Fatigue, weight change, feeling cold or hot, hair loss or constipation
- Anxiety, palpitations or tremor
- Irregular periods or trouble conceiving
- A family history of thyroid disease
- Abnormal thyroid results you want explained
See a medical provider promptly for a racing or irregular heartbeat, severe confusion or drowsiness, a rapidly growing neck lump, or trouble swallowing or breathing.
Want help making sense of your labs?
A free 15-minute consultation with Dr. Kneessi. No cost, no obligation. In-office in Odenton, MD or by telehealth.
Frequently asked questions
What does high TSH mean?
Usually an underactive thyroid.
What does low TSH mean?
Usually an overactive thyroid or too much medication.
Is TSH enough to check my thyroid?
It is a good screen, but free T4, free T3 and antibodies add detail when symptoms persist.
Does TSH change during the day?
Yes. It is usually higher in the early morning.
Sources
- Bianco AC, et al. Paradigms of dynamic control of thyroid hormone signaling. Endocr Rev 2019. PMID: 31033998. https://pmc.ncbi.nlm.nih.gov/articles/PMC6596318/
- Russell W, et al. Free triiodothyronine has a distinct circadian rhythm that is delayed but parallels thyrotropin levels. J Clin Endocrinol Metab 2008. PMID: 18364382. https://pubmed.ncbi.nlm.nih.gov/18364382/
- Li D, et al. Association of biotin ingestion with performance of hormone and nonhormone assays in healthy adults. JAMA 2017. PMID: 28973622. https://pmc.ncbi.nlm.nih.gov/articles/PMC5818818/
- Leung AM, Braverman LE. Consequences of excess iodine. Nat Rev Endocrinol 2014. PMID: 24342882. https://pmc.ncbi.nlm.nih.gov/articles/PMC3976240/
- Ventura M, Melo M, Carrilho F. Selenium and thyroid disease: from pathophysiology to treatment. Int J Endocrinol 2017. PMID: 28255299. https://pmc.ncbi.nlm.nih.gov/articles/PMC5307254/
- Van den Berghe G. Non-thyroidal illness in the ICU: a syndrome with different faces. Thyroid 2014. PMID: 24845024. https://pmc.ncbi.nlm.nih.gov/articles/PMC4195234/
- MedlinePlus: TSH (Thyroid-Stimulating Hormone) Test
- NIDDK: Thyroid Tests
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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