The thyroid gland is located in the front of the neck, below the larynx (voice box). The small, two-inch gland consists of two lobes, one on each side of the windpipe, connected by tissue called the isthmus.
The thyroid tissue is made up of two types of cells: follicular cells and parafollicular cells. Most of the thyroid tissue consists of the follicular cells, which secrete iodine-containing hormones called thyroxine (T4) and triiodothyronine (T3). The parafollicular cells secrete the hormone calcitonin. Parafollicular cells do not make thyroid hormone and do not have the ability to absorb iodine.
The thyroid needs iodine to produce thyroid hormones. The follicular cells of the thyroid have channels or pores to actively absorb iodine for making thyroid hormone. The majority of iodine comes from our diet, both processed foods and iodinated salt.
The thyroid plays an important role in regulating our body's metabolism. The T4 and T3 hormones stimulate every tissue in the body to produce proteins and increase the amount of oxygen used by cells. Thyroid hormones help regulate our heart rate, blood pressure, energy level, how efficiently we use calories, and how warm or cold we feel. In young children, thyroid hormones are critical for brain development and growth.
The calcitonin hormone works together with the parathyroid hormone (a protein hormone secreted by cells in the parathyroid glands) to regulate calcium levels in the body.
During pregnancy, thyroid hormone is critical for normal brain development of the baby.
Under normal conditions an area of the brain called the pituitary gland secretes a hormone called thyroid stimulating hormone (TSH) that tightly controls the amount of thyroid hormone produced. The system is designed as a feedback loop where the pituitary senses how much thyroid hormone is being released by the thyroid and adjusts the amount by making more or less TSH. An elevated TSH with a low or low-normal thyroid hormone level is called hypothyroidism (too little thyroid hormone), and a low or suppressed TSH with an elevated thyroid hormone level is called hyperthyroidism (too much thyroid hormone).
Other thyroid disorders include:
Thyroid disorders may be congenital (present at birth), or develop later in childhood. With proper treatment most thyroid disorders can be successfully managed in children.