TSH
Also called Thyroid-stimulating hormone, thyrotropin
TSH (thyroid-stimulating hormone, also called thyrotropin) is a hormone made by the pituitary gland at the base of the brain that tells the thyroid how much thyroid hormone to produce. The thyroid makes two hormones, thyroxine (T4) and triiodothyronine (T3), which control how the body uses energy.
The relationship runs in reverse, which is what makes TSH useful. When thyroid hormone in the blood is low, the pituitary releases more TSH to push the thyroid harder; when it is high, TSH falls. A TSH test shows whether the thyroid is under- or overactive, but not why, so an abnormal result is usually followed by a free T4 test and sometimes by free T3 or thyroid antibodies. What a given result means, and why a normal TSH does not settle every complaint, is covered in TSH, Free T4 and Free T3: What Each One Measures.
Why it matters after 45
An underactive thyroid is more common in women and in people over 60, and its symptoms (fatigue, weight gain, feeling cold, joint aches, dry or thinning hair, low mood) overlap heavily with complaints people put down to midlife or menopause. In adults over 60, an overactive thyroid can also look different, sometimes as poor appetite or withdrawal rather than the classic racing heart. That overlap is why TSH is one of the first markers checked when energy, weight or mood shift.
Where it comes up
Related terms
References
- MedlinePlus. TSH (Thyroid-stimulating hormone) Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/tsh-thyroid-stimulating-hormone-test/
- National Institute of Diabetes and Digestive and Kidney Diseases. Thyroid Tests. https://www.niddk.nih.gov/health-information/diagnostic-tests/thyroid
- National Institute of Diabetes and Digestive and Kidney Diseases. Hypothyroidism (Underactive Thyroid). https://www.niddk.nih.gov/health-information/endocrine-diseases/hypothyroidism
Definitions here are educational and are not medical advice. They explain what a term means; the pages linked above cover what it means for you, and a clinician reviews your own results. Editorial & medical review policy · All glossary terms