What Is Hypothyroidism In Children?

Hypothyroidism in children is a condition in which there is too little thyroid hormone in the bloodstream. The thyroid gland, which produces the thyroid hormones, is said to be "underactive," because it produces too little thyroid hormone needed for the body to function normally. Hypothyroidism can affect adults as well.

• Infants and small children affected by hypothyroidism may have significant problems with growth and development if it not diagnosed and treated promptly.

• In older children and young adults, hypothyroidism can cause diverse symptoms due to lack of thyroid hormone, including slowed heart rate, chronic tiredness, inability to tolerate cold, mental fatigue and difficulty in learning, and constipation.

Hypothyroidism can develop at any point in the lifespan. Infants can be born with hypothyroidism, and hypothyroidism can develop in children and adults of any age.

Nice To Know: About the thyroid gland The thyroid is a small, butterfly-shaped gland that lies just under the Adam's apple in the neck. There are two lobes to the gland, and they lie just in front and at either side of the windpipe (trachea). The thyroid is part of the body's endocrine system, which consists of glands that secrete hormones into the bloodstream. The thyroid gland secretes thyroid hormones, which control the speed at which the body's chemical functions proceed (metabolism). To produce thyroid hormones, the thyroid gland needs iodine, an element contained in many foods. The thyroid gland also produces a hormone, called calcitonin, which may be involved in the metabolism of bones.

What Is Thyroid Hormone?

Hormones are chemical messengers released into the bloodstream by specialized glands called endocrine glands. A hormone circulates through the body in the bloodstream, delivering messages to other parts of the body. The "message" causes effects far from the gland that produced the hormone.

Thyroid hormone is produced in the thyroid gland, which is located in the front of the neck. It is released by the thyroid gland into the bloodstream and circulates throughout the body. Almost every cell in the body, from those in the brain to those in the feet, responds to the hormone.

There are two different forms of thyroid hormone present in the bloodstream. The two forms of thyroid hormone differ in the number of iodine units or atoms attached to the hormone. Iodine is a very important component of thyroid hormone.

• Thyroid hormone with four iodine units is abbreviated as T4

• Thyroid hormone with three iodine units is abbreviated as T3

• Most thyroid hormone in the blood is T4.

• T3 is the form that is active in the body, not T4.

• Certain cells in the body convert T4 to T3.

What Does Thyroid Hormone Do?

Cells respond to thyroid hormone with an increase in metabolic activity. Metabolic activity, or metabolism, is a term used to describe the processes in the body that produce energy and the chemical substances necessary for cells to grow, divide to form new cells, and perform other vital functions.

If you think of each cell in the body as a motorcar, then thyroid hormone acts as if you were tapping on the accelerator pedal. Its message is "go."

• Because thyroid hormone stimulates cells, cells grow and divide and major body functions go a bit faster.

• Use of proteins, fats, and carbohydrates increases, heart rate and breathing rate increase, and muscle tone becomes more brisk in both skeletal muscles and muscles in the digestive system.

But if there's not enough thyroid hormone, the body slows down, like taking one's foot off the accelerator pedal. Thus in children:

• Growth and development are delayed; in some areas, such as brain development, hypothyroidism may cause severe, permanent effects.

• In older children and young adults, the decrease in organ function associated with hypothyroidism causes noticeable symptoms: The heart beats more slowly, muscle tone slows, the child may feel physically tired and mentally fatigued, and learning may be impaired.

How Are The Blood Levels Of Thyroid Hormone Controlled?

Normally, the body runs like a car on cruise control-functioning at a steady rate. This steady state is known as homeostasis. The body's control system that regulates the cells to function at a steady, appropriate metabolic rate may be explained as follows:

• Special "detector" cells in the brain monitor the level of thyroid hormone in the blood.

• When the level of thyroid hormone drops, these cells send signals to a nearby organ in the brain known as the pituitary gland.

• These signals stimulate the pituitary gland to release a substance called thyroid-stimulating hormone (TSH) into the bloodstream.

• TSH signals cells in the thyroid gland to release more thyroid hormone into the bloodstream.

• When the blood level of thyroid hormone has increased enough, the detector cells in the brain detect the increase in thyroid hormone level.

• These detector cells send signals to the pituitary gland to stop release of TSH.

Why Is The Thyroid Gland Called An Endocrine Gland?

A number of glands in the body produce hormones, chemicals that are released into the blood and circulate throughout the body. The thyroid gland, as well as these other glands, is called an endocrine gland. Because endocrine glands release homrones into the blood, the homrones can have effects far from the gland that produced it. Growth hormone, for instance, is produced in the pituitary gland, which is located underneath the brain. Yet almost every cell in a child's body, from those in the brain to those in the foot, responds to both growth hormone and thyroid hormone.