The thyroid gland is a 2 inch long, butterfly shaped organ located in the front lower part of the neck. It is responsible for the production, storage and release of two main hormones called Triiodothyronine (T3) and Thyroxine (T4).
The hypothalamus and the pituitary gland in the brain is responsible for the production of T3 and T4. The hypothalamus produces a TSH releasing hormone called thyrotropin-releasing hormone (TRH) that signals the pituitary gland to produce TSH. The release of TSH by the pituitary gland regulates the production of hormones in the thyroid gland i.e., T3 and T4.
In case of low T3 and T4 levels, the pituitary gland releases more of TSH, that stimulates the thyroid hormone to produce more of T3 and T4.
In case of high T3 and T4 levels, the pituitary gland reduces the release TSH, that makes the thyroid hormone produce less of T3 and T4.
The thyroid gland absorbs iodine from the blood and incorporate it into the thyroid hormones. These hormones are responsible for controlling the rate of metabolism in the body. The metabolic rate of the body influences the heart, muscle and digestive function, brain development and bone maintenance. The key to the thyroid hormone is the amount of iodine in our meal. The thyroid gland absorbs the iodine from the blood and incorporate it into the thyroid hormones.
In addition, there are other hormone-producing cells within the thyroid gland called C-cells. These cells produce calcitonin. Calcitonin plays a role in regulating calcium and phosphate levels in the blood, which is important for your bone health and maintenance.
In normal cases thyroid gland produces the exact number of hormones needed to keep the body’s metabolism running and in balance. However, there are several disorders. When the thyroid gland produces too much of T3 and T4, it leads to higher metabolism, excess weight loss, fast heart rate, high irritability/nervousness, muscle weakness and tremors, infrequent menstrual periods and sleep problems. This condition is caused by a hyperactive thyroid gland and hence is called hyperthyroidism. Whereas, when the thyroid gland produces lower amounts of T3 and T4, it leads to lower metabolism rate. Low metabolism leads to depression, weight gain, slower heart rate, fatigue, more frequent and stronger menstrual periods, forgetfulness, dry skin and hair, hoarse voice and intolerance to cold. This condition is caused by an under active thyroid gland and hence is called hypothyroidism.