What is hypothyroidism?
The thyroid is the largest endocrine gland in the body. It sits just below the larynx (voice box) and wraps around the trachea (windpipe). The thyroid gland produces thyroid hormone, which helps the body grow and develop. It also plays an important role in the body's metabolism (the processes in the body that use energy, such as eating, breathing, and regulating heat).
Hypothyroidism (or underactive thyroid) is a common condition in which the thyroid gland makes too little thyroid hormone. About 1 in 5,000 babies is born with congenital hypothyroidism, in which the thyroid fails to grow normally and cannot produce enough hormone. There is no known cause for most cases of congenital hypothyroidism. But about 10 to 20 percent of the time, the condition is caused by an inherited defect that alters the production of thyroid hormone.
The most common inherited form of hypothyroidism is a defect of the TPO (thyroid peroxidase) gene on chromosome 2. This gene plays an important role in thyroid hormone production.
How do people get hypothyroidism?
Hypothyroidism may be caused by (1) an autoimmune disease that attacks the thyroid gland, (2) surgery or radiation to treat thyroid cancer and other conditions, or (3) rare and random genetic events in which a mutation is acquired during early embryonic development.
What are the symptoms of hypothyroidism?
In babies with the inherited form of hypothyroidism, the condition affects growth and cognitive development. It may cause intellectual disability, delayed puberty, stunted growth, and ataxia (uncoordinated muscle movements).
In adults, hypothyroidism slows the body's metabolism, making the patient feel mentally and physically sluggish. Symptoms may include weakness, fatigue, muscle aches, mood swings, hair loss, memory loss, or slow speech. A person's symptoms will depend upon how little thyroid hormone they make, and for how long they have had the disorder.
When the body has too little thyroid hormone, the pituitary gland works overtime, making extra thyroid-stimulating hormone (TSH). Having too much TSH may enlarge the thyroid, forming a goiter.
How do doctors diagnose hypothyroidism?
Babies are normally screened for hypothyroidism 24 hours after birth. A tiny sample of blood taken from the baby's heel is tested for low thyroid hormone levels or high thyroid-stimulating hormone (TSH) levels.
How is hypothyroidism treated?
Hypothyroidism is treated with hormone replacement therapy: people with hypothyroidism must take a synthetic form of thyroid hormone every day to reduce their symptoms. When treatment is started right away, babies develop normally.