What are pediatric thyroid disorders?

Under normal conditions an area of the brain called the pituitary gland secretes a hormone called thyroid stimulating hormone (TSH) that tightly controls the amount of thyroid hormone produced. The system is designed as a feedback loop where the pituitary senses how much thyroid hormone is being released by the thyroid and adjusts the amount by making more or less TSH.

An elevated TSH with a low or low-normal thyroid hormone level is called hypothyroidism (too little thyroid hormone. A low or suppressed TSH with an elevated thyroid hormone level is called hyperthyroidism (too much thyroid hormone).

The most common thyroid disorders in children are:

• Hypothyroidism
• Hyperthyroidism, also called Graves disease
• Thyroid nodules
• Differentiated thyroid cancer
• Multiple endocrine neoplasia type 2
• Medullary thyroid cancer

Less common thyroid conditions that can affect children include:

• DICER1 syndrome
• Familial adenomatous polyposis
• PTEN hamartoma tumor syndrome

Thyroid disorders may be inherited or occur sporadically. Symptoms can be present at birth or develop later in childhood. With proper treatment, most thyroid disorders can be successfully managed in children.

Thyroid anatomy and function

The thyroid gland is located in the front of your child’s neck, below the larynx (voice box). The small, two-inch gland consists of two lobes, one on each side of your child’s windpipe, connected by tissue called the isthmus.

Your child’s thyroid is made up of two types of cells: follicular cells and parafollicular cells. Most of the thyroid tissue consists of the follicular cells, which secrete iodine-containing hormones called thyroxine (T4) and triiodothyronine (T3).

The parafollicular cells secrete a hormone called calcitonin. Parafollicular cells do not make thyroid hormone and do not have the ability to absorb iodine.

Your child’s thyroid needs iodine to produce thyroid hormones. The follicular cells of the thyroid have channels — or pores — to actively absorb iodine and to make thyroid hormone. The majority of iodine used to create thyroid hormone comes from your child’s diet of processed foods and iodinated salt.

Role of thyroid hormones

The thyroid plays an important role in regulating your child’s metabolism. The T4 and T3 hormones stimulate every tissue in your child’s body to produce proteins and increase the amount of oxygen used by cells.

Thyroid hormones help regulate your child’s heart rate, blood pressure, energy level, how efficiently they use calories, and how warm or cold they feel. In young children, thyroid hormones are critical for brain development and growth.

The calcitonin hormone — from the parafollicular cells in the thyroid — works with the parathyroid hormone (a protein hormone secreted by cells in the parathyroid glands) to regulate calcium levels in your child’s body.

During pregnancy, thyroid hormone is critical for normal brain development of the baby.