Disorders Affecting the Thyroid
The thyroid gland, located in the front of the neck and below the larynx, plays an important role in regulating the body’s metabolism and calcium balance. The small, two-inch gland consists of two lobes, connected by tissue called the isthmus. The thyroid tissue 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 iodinecontaining hormones called thyroxine (T4) and triiodothyronine (T3), which regulate metabolism. The parafollicular cells secrete the hormone calcitonin. The thyroid needs iodine to produce the hormones.
Levels of hormones secreted by the thyroid are controlled by the pituitary gland’s thyroid-stimulating hormone, which, in turn, is controlled by thyrotropin-releasing factor (TRF) from the hypothalamus.
A thyroid disorder may be congenital, or develop later in childhood. With proper treatment, which usually involves hormone replacement therapy, most thyroid disorders can be successfully managed in children.
One of the most common endocrine problems of childhood. It is either congenital or acquired. It is rarely occur from dietary insufficiency of iodine because of the iodized salt. Impaired growth and development are less when hypothyroidism is acquired at a later age and because brain growth is nearly complete by 2-3 years mental retardation and neurologic sequelae are not associated with juvenile hypothyroidism.
Hypothyroidism is the condition in which the thyroid is underactive and is producing an insufficient amount of thyroid hormones. The deficiency of TH present at birth. Hypothyroidism is the most common thyroid disorder. However, children with the disorder display different symptoms from adults.
Hypothyroidism in the newborn, when left untreated can lead to mental retardation.
The disorder may be permanent or transient:
– Permanent CH results from (1) defective thyroid gland development, (2) enzymatic defect in thyroxine synthesis or (3) pituitary dysfunction.
– Transient hypothyroidisim results from intrauterine transfer of goiter-inducing substances (antithyroid drugs and expectorants given for asthma) which inhibit thyroid secretion.
Many preterm infants have hypothyroidism at birth as a result of hypothalamic and pituitary immaturity.
Hypothyroidism is self-limiting disease, but may be fatal.
Severity depends on the amount of thyroid tissue present. Newborn usually does not exhibit obvious signs of hypothyroidism, probably because of the exogenous source of prenatal thyroid hormone supplied by maternal circulation.
The symptoms of hypothyroidism in children are different than in adults. Each child may experience symptoms differently, and often the symptoms are not seen at all. This is why all infants should be screened for low thyroid. Symptoms may include:
Shorter after birth
· poor feeding
· prolonged jaundice
· respiratory difficulty
· hoarse cry
· large fontanels
Infants with CH may be born postterm > 40 weeks or have a birth weight over 4 kg.
An untreated CH classic feature appears after around 6 weeks of life and includes:
· typical facial features: depressed nasal bridge, short forehead, puffy eyelids and large tongue
· thick, dry, mottled skin that feel cold
· coarse, dry, dull hair
· abdominal distention
· umbilical hernia
· hypothermia, hypotesion and narrow pulse pressure
· anemia, widely patent cranial sutures
· retarded bone age: slow growth, sometimes resulting in abnormally short limbs
· delayed tooth development
· Most serious consequence is delayed development of nervous system, which leads to mental retardation. The severity of intellectual deficit is related to the degree of hypothyroidism and the duration of the condition before treatment.
· Other nervous system manifestations: slow, awkward movements and abnormal deep tendon reflexes.
Neonatal screening for T4 and then TSH
With CH: low level of T4 (< 6mg/dl), high level of TSH (> 50 μIU/ ml) + Bone age
Treatment of hypothyroidism:
Left untreated in newborns, hypothyroidism can lead to mental retardation. Untreated hypothyroidism may also lead to anemia, low body temperature, and heart failure. The goal of treatment is to restore the thyroid gland to normal function, producing normal levels of thyroid hormones. Treatment may include prescription of thyroid hormones to replace the deficient hormones. The drug of choice is Synthetic Levothyroxine Sodium. Some children will require hormone replacement therapy for the rest of their lives, while others appear to outgrow the disorder, often by the age of 3. Regular monitoring of the child’s thyroid hormone levels during the course of treatment, including a 30-day discontinuation of treatment to see how the thyroid responds, can help the child’s physician diagnose the condition more accurately.
– Early identification of the disorder: parental remarks of unusually “good & quite” baby & screening
– Education about lifelong treatment
– The medicine of CH is tasteless, thus it can be crushed and added to formula, water or food
– If a dose is missed, twice the dose should be given the next day
– Signs of overdose: rapid pulse, dyspnea, irritability, insomnia, fever, sweating, weight loss
– Genetic counselling if the disorder was inborn error
It is an enlargement or hypertrophy of the thyroid gland. It may occur with deficient (hypothyroid), excessive (hyperthyroid) or normal (euthyroid) TH secretions.
Goiter is either congenital or acquired. Congenital goiter occurs as a result of maternal administration of antithyroid drugs or iodides during pregnancy. Acquired goiter results from increased secretion of pituitary TSH in response to decreased circulating levels of TH or from infiltrative neoplastic or inflammatory processes.
Enlargement of the thyroid gland may be mild and noticeable only when there is an increased demands for TH (during period of rapid growth)
Enlargement of the thyroid gland at birth can be sufficient to cause severe respiratory distress.
Hyperthyroidism (Graves Disease)
Hyperthyroidism means overactivity of the thyroid gland, resulting in too much thyroid hormone in the bloodstream. The over-secretion of thyroid hormones leads to overactivity of the body’s metabolism. In newborns, the most common cause of an overactive thyroid is called neonatal Graves disease, which can be life threatening. However, hyperthyroidism rarely occurs in children and adolescents.
In newborns, the cause of hyperthyroidism is a mother who has or has had Graves disease herself. Graves disease in adults is an autoimmune disorder characterized by the production of antibodies that stimulate the thyroid gland. When a pregnant woman has these antibodies, they can cross the placenta and affect the fetus’ thyroid gland. Graves disease in pregnant woman can result in stillbirth, miscarriage, or premature birth.
Symptoms of hyperthyroidism:
The following are the most common symptoms of hyperthyroidism in a newborn. However, each baby may experience symptoms differently. Symptoms may include:
· poor weight gain/ gradual loss, muscle weakness
· cardiac manifestations: tachycardia (rapid pounding pulse which can lead to heart failure), high blood pressure
· Tremors, insomnia.
· nervousness, emotional lability
· irritability, hyperactivity
· bulging/ protruding eyeballs (Exophthalmos)
· hyper activity of GIT/ vomiting & diarrhea
· short attention span
· skin: warm, flushed and moist
· heat intolerance accompanied by diaphoresis.
· difficulty breathing due to enlarged thyroid gland (goiter)
Prolonged exposure to high levels of the thyroid-stimulating antibodies characteristic of hyperthyroidism can pose serious health problems to an infant later in childhood, including the following:
· premature closing of fontanel’s
· mental retardation
· slowed growth
Diagnosis based on increased levels of T4 and T3 with suppressed TSH
Treatment for hyperthyroidism:
With prompt treatment, babies usually recover completely within a few weeks. However, hyperthyroidism may recur during the first 6 months to 1 year of life. The goal of treatment is to restore the thyroid gland to normal function, producing normal levels of thyroid hormone. Treatment may include:
· medication that blocks the production of thyroid hormones; antithyroid drugs such as propylthiouracil (PTU) & methimazole (MTZ)
· subtotal thyroidectomy
· ablation with radioiodine (131 I-iodide)
• Identify children with hyperthyroidism
• Alert for signs and symptoms
• Child needs quiet environment, rest periods
• Help family cope with emotional lability associated with disorder
• Dietary requirements to meet child’s increased metabolic rate
• Medications: side effects (skin rash, drug fever, hepatitis, edema of lower extremities, decreased sense of taste, cervical lymphadenopathy, leukopenia)