Thyroid stimulating hormone (TSH) is one of a series of regulatory hormones to come from the pituitary gland, often called the “master gland“ of the body. Most of the pituitary hormones are released upon signals from the hypothalamus, part of the real master coordinator of the body, the brain.
TSH Instructs the Thyroid gland to produce more Thyroid hormone. When more Thyroid hormone is produced, The increase of Thyroxin in the bloodstream causes the TSH level to drop.
Our metabolism is full of these servomechanisms which control the level of critical substances. When the thyroid does not function properly, and the thyroid level drops, the TSH is increased. An elevated TSH it is presently the best test we have for hypothyroidism.
Conversely, when there is excessive thyroid activity (hyperthyroidism), the TSH level drops to vanishingly low amounts. Tomorrow the subject will be thyroxin.