What is the thyroid ?
The thyroid gland is organized around little follicles. The thyroid cells called thyrocyts capture the Iodine element in the blood. In the tyroid cells there is a protein called TPO for thyroperoxydase which is in charge of activating the Iodide in Iodine. This protein is very important.
In the thyroid gland there is an other protein (yes I know it makes a lot of protein) called this time the thyroglobulin. But what is the job of this thyroglobulin ? This thyroglobulin is synthetized by the thyrocyts and contain tyrosin residues. (Tyrosin is an amino acid used to make proteins, let’s imagine that proteins are a pearl necklace then in that example amino acid would be the pearl). The thyroglobulin with Iodine is going to make the thyroid hormones called T3 (triiodothyronin) and T4 (thyroxine)
So basically, thyroglobulin + Iodine = T3 and T4
Those 2 hormones : T3 and T4 are being released in blood circulation.
Food Intake
The daily need of Iodine are 100 to 150 μg a day, which are very little need, easily fulfilled. Iodine can be found in marine products, milk and vegetables.
The salt in also very rich in Iodine.
Thyroid hormones regulation
So, the thyroid secretion of T3 and T4 are regulated by TSH hormone which is helself regulated and controlled by TRH. I know, it’s a lot to apprehend so let’s take things back slowly.
What are the TRH and TSH Hormone ?
The TRH (thyrotropin releasing hormon) is secreted by the hypothalamus which is located at the base of the brain.
The TRH go in a network of little capillaries and then reach the pituitary gland. Then the TRH stimulates the secretion of TSH by the pituitary gland. Then the TSH acts on the thyroid and regulates the T3 and T4 secretion. It’s called Hypothalamic–pituitary–adrenal axis and it’s a rectrocontrol system : when T3 and T4 levels goes up, it’s inhibits the secretion of TRH and TSH, to make the T3 and T4 go down and stay regulated. Here is a little schema to better understand everything as it’s a little complex.
A French Pharmacist in Paris 