The thyroid produces a hormone called thyroxine, which affects every bodily system by signaling how fast or slow it should be working. Hyperthyroidism is a condition where the thyroid produces too much of this protein. MedlinePlus, an online medical encyclopedia, indicates that a hyperactive thyroid may affect adults, infants and children.
Newborns
Hyperthyroidism in newborns is usually caused by a condition in the mother called Graves' disease. Autoantibodies that stimulate the thyroid to produce too much thyroxine cross the placenta, and also stimulate the infant's thyroid. These antibodies persist in the infant for varying lengths of time; as long as they do persist, they cause hyperactivity of the thyroid in infants. Merck Manuals, an online medical library, indicates that this condition may be especially serious in infants, causing death in 10 to 15 percent of the newborns affected. Symptoms of infants affected by a hyperthyroidism include, according to Merck Manuals: feeding problems, irritability, high blood pressure, bulging eyes, microcephaly (an excessively small head). The Children's Hospital Boston confirms these symptoms, and lists other symptoms: diarrhea, vomiting, poor weight gain, fast heart beat and nervousness. A large thyroid may also cause difficulty breathing in infants. While symptoms in the newborn usually clear up within 6 months of birth, long-term hyperthyroidism may cause additional complications as the infant grows into a child.
Children: Growth Problems
If the child has a condition that increases the output of the thyroid, such as Graves' disease, he may also experience other symptoms associated with hyperthyroidism. The Children's Hospital Boston reports that hyperthyroidism in children can cause growth problems, resulting in reduced height and weight.
Children: Other Symptoms
If hyperthyroidism is especially severe, problems other then those affecting growth may occur. These symptoms, according to Merck Manuals, include impaired intellect, hyperactivity and craniosynostosis (where the cranial sutures fuse prematurely). The child may be affected with some of the same symptoms as adults. These common symptoms, according to MedlinePlus include difficulty concentrating, fatigue, intolerance of heat, increased appetite, increased sweating, weight loss and the presence of a goiter. MedlinePlus reports that hyperthyroidism may also cause a delay in puberty.
