It produces hormones that help control your heart and digestive system.
In infants, thyroid hormones help the brain and bones develop.
The thyroid produces and releases two major hormonesthyroxine (T4)andtriiodothyronine (T3).
Verywell / Jessica Olah
Roughly 10 times that amount of T4, about 1000 mcg, is constantly circulating in your blood.
The remainder is converted toreverse T3(rT3)by cleaving off an iodine atom from a different location.
The thyroid’s active hormone is T3, while rT3 is completely inactive.
T3 is degraded much more rapidly than T4.
T3 does this by binding to a cells DNA.
This bound T3 causes nuclear DNA to stimulate (or inhibit) the production of specific proteins.
This is certainly true when it comes to the thyroid, which is part of the endocrine system.
So, as T3 blood levels increase, TSH levels fall.
This feedback loop operates to keep the production of thyroid hormone by your thyroid gland within a narrow range.
Any of these conditions are potentially very serious.
Symptoms
Thesymptoms of thyroid diseasecan be quite variable from individual to individual.
Indiagnosing a thyroid disorder, assessing the pituitary-thyroid relationship is particularly critical.
In some cases, the proper interpretation of TSH levels can be tricky and controversial.
However, in rare instances high TSH levels could also be related to a pituitary tumor.
National Library of Medicine.How Does The Thyroid Gland Work.
U.S. Department of Health and Human Services, Office on Women’s Health.Thyroid Disease.
Mullur R, Liu YY, Brent GA.Thyroid hormone regulation of metabolism.Physiol Rev.
2020;43(1):31-41. doi:10.1007/s40618-019-01084-9
Johns Hopkins University.Goiter.
National Library of Medicine, National Institutes of Health.Hypothyroidism.
National Library of Medicine, National Institutes of Health.Hyperthyroidism.
National Library of Medicine, National Institutes of Health.Thyrotropin-Secreting Pituitary Adenomas.
National Library of Medicine, National Institutes of Health.Pituitary Hyperplasia In Primary Hypothyroidism.
Brent GA.Mechanisms of Thyroid Hormone Action.The Journal of Clinical Investigation.
2012;122(9):30353043. doi:10.1172/JCI60047.
2014;24(12):16701751. doi:10.1089/thy.2014.0028.
Mullur R, Liu Y-Y, Brent GA.Thyroid Hormone Regulation of Metabolism.Physiological Reviews.
2014;94(2):355382. doi:10.1152/physrev.00030.2013.
