The Thyroid is a small gland that looks like a butterfly, sitting across the front of my neck, riding my windpipe (trachea), just below my “Adam’s apple” (larynx).
That butterfly has 2 big wings (the 2 lobes) and a small body (the isthmus) between these 2 wings.
It produces hormones that accelerate the chemical reactions in the body.
The abundant hormone produced by the thyroid is “T4” (thyroxine). As most other hormones, it is carried by blood from its factory (the thyroid) to the rest of the body where it works. However, as it is, it can’t work right away; it has to be converted in the rest of the body (especially in the liver) to another hormone, “T3”, which is the ultimately active thing that does the thyroid work in the body.
A little bit of T3 is made by the thyroid, the rest of it is made by the body outside the thyroid by conversion of T4. Such conversion sometimes is not up to par. Therefore, thyroid hormones could look normal in the blood (mostly made up of T4), while the active form that really works inside the cells of the rest of the body parts, T3, is not enough. So, sometimes I feel bad, while my blood test looks good..
Thyroid uses Iodine to make its hormones. It uses up to 80% of the Iodine I take everyday. If I don’t get enough Iodine in my food, I could get a deficiency in my thyroid hormones (Hypothyroidism). If I take too much Iodine, my thyroid could make either too much of its hormones (Hyperthyroidism), or paradoxically too little of them (Hypothyroidism) in certain circumstances.
Thyroid is watched all the time by the pituitary gland (a small gland in my brain). It does that by sending a hormone called “Thyroid Stimulating Hormone (TSH) to stimulate the thyroid when necessary. When the pituitary feels there are too little thyroid hormones in the blood, it sends more of the TSH to whip the thyroid to produce more of its hormones. On the other hand, when the pituitary gland sees too much thyroid hormone in the blood, it decreases or shuts off its TSH, because the thyroid needs no stimulation, it is already fired up. So, TSH goes in a reverse way to the thyroid. No wonder, sometimes the doctor tells me that my blood test (TSH) is high, and that it means I have low thyroid (and the other way round). Confusing, Huh!
To put the pituitary thing in a different way, one can imagine the thyroid gland as a furnace, the pituitary gland as its thermostat, and thyroid hormones as the heat. When it is cold (the thyroid hormone levels drop), the thermostat sends a signal to the furnace (TSH increases) to turn it on to produce heat (thyroid hormones).When there is too much heat, the thermostat sends a signal (less TSH) to the furnace to turn it off.