The thyroid is a gland in the neck that regulates the production and distribution of hormones throughout the body that are responsible for the proper functioning of cells. Children who have an underactive thyroid, known as hypothyroidism, are deficient in necessary thyroid hormones. Those with an overactive thyroid, known as hyperthyroidism, have too much thyroid hormone in their bodies. A baby may be born without a thyroid gland or with an underdeveloped thyroid gland, or a child may inherit a thyroid disorder from family members.
Children suffering from hypothyroidism may have a lack of energy and experience excessive fatigue. They may have poor circulation due to a slowed heartbeat, which can lead to a low body temperature and a general feeling of being cold. Because of the lack of thyroid hormone in the body, children with hypothyroidism may have brittle hair that breaks easily; dry, pale or yellow skin; or suffer from bouts of constipation. Physical development may also be delayed as a result of an underactive thyroid, leaving children shorter than normal when compared to peers. In some instances, puberty may not be reached until the thyroid disease is properly treated. Infants with hypothyroidism may show few signs of the disorder. Those who do have symptoms may have a large, protruding tongue, puffy face, yellowing of the skin and eyes and may experience frequent choking, according to the Mayo Clinic.
Hyperthyroidism in children can increase their heart rate, making them feel jumpy and on edge. The increased heart rate can also make it difficult for a child to concentrate on anything for any length of time. Unlike hypothyroidism, an overactive thyroid may cause a child to sweat or tremble and can also make it difficult for a child to sleep. Children with an overactive thyroid may have an increased appetite but, at the same time, may experience weight loss. Some children have a wide-eyed stare as if they are frightened, or it may appear that their eyes are bulging.
A goitre may be present in cases of both hypothyroidism and hyperthyroidism. A goitre develops when the thyroid gland swells and protrudes from the neck. In some instances, a lump, called a nodule, may begin to grow on the thyroid gland, indicating a thyroid disorder.