Thyroid disorders are among the commonest of the endocrine disorders. The thyroid gland is normally situated in the front of the neck below the voice box. The thyroid gland produces thyroid hormones which have an effect on virtually every organ in the body.
Thyroid hormones regulate the body’s thermostat making bodily functions speed up when over active and slow down when the thyroid is underactive.
Disorders of the thyroid can be grouped into those that cause the thyroid to be enlarged (goiter) or shrunken away. The thyroid can be overactive and produce too much thyroid hormone (hyperthyroid) or it can produce too little hormone (hypothyroid).
The most common cause of an overactive thyroid is Graves disease an autoimmune condition in which antibodies that target the TSH receptor on the thyroid and result in overstimulation of the thyroid. This leads to overproduction of thyroid hormones, T4 and T3 as well as increase in the size of the thyroid gland or goiter. This condition can be treated medically with Neomercazole to cause remission or more permanent options including treatment with radioactive iodine or very rarely surgery are available.
The most common cause of an underactive thyroid is Hashimoto’s thyroiditis also called chronic lymphocytic thyroiditis. Again the thyroid is attacked by the immune system. This is one of the most common autoimmune conditions, it is often passed on along the maternal line and many family members can be affected. The body mounts both a cell mediated and a humoral (antibody) attack on the thyroid gland. Over time this leads to the thyroid failing. During the early attack the thyroid can release stored thyroid hormones, resulting in a brief period of thyroid hormone excessive before eventual deficiency this condition is known as Hashitoxicosis. The thyroid gland can enlarge though stimulation by TSH as it fails and also through invasion by cells involved in the cell mediated immune attack.
A problem can be suspected because of symptoms related to too much or too little thyroid hormone, or to an enlargement or pain in the thyroid gland.
Thyroid tumours are rare in children and adolescents but need to be considered if there is a family history of endocrine or thyroid tumours. The thyroid gland will typically have a nodule, or be asymmetrically enlarged.
A separate group consists of congenital thyroid problems or congenital hypothyroidism-where babies are born with underactive thyroid glands. This condition should be routinely screened for as part of the newborn screening protocol. Early diagnosis and treatment are essential to protect the babies developing brain.
If the thyroid gland does not produce enough thyroid hormone it can be supplemented or fully replaced with thyroxine- trade names include Eltroxin, Euthyrox and Synthroid. Very occasionally tertroxin or diotroxin may be needed. Thyroid replacement is often needed for the remainder of your life.
Typical thyroid investigations include a thyroid function test with antibodies, an ultrasound and sometimes a nuclear medicine uptake scan with iodine or technetium. The adequacy of replacement is measured by performing thyroid function tests – including a TSH, Free T4 and if the thyroid is overactive a Free T3. TSH receptor antibodies or Thyroid stimulating antibodies can be used to confirm the diagnosis of Graves disease.