Neonatal Hypothyroidism - An Insight

Introduction

The thyroid gland is situated in the neck in the lower front region and is shaped like a butterfly. It produces thyroid hormone, which is released in the blood. The thyroid hormone maintains body temperature and metabolism and is essential for the functioning and development of the organs. The thyroid hormone has a crucial role in developing the child's brain. It enables the body to use the energy, function of the organs, and child development. In addition, the thyroid hormone is essential for the development of the hypothalamic-pituitary part of the brain. Thyroid hormones play an important role in synapsis development, myelination (layer wrapping the neurons), and neuronal differentiation. After the birth of a child, there is detachment of the placenta, and a temperature change occurs. Due to thermal changes, the rapid circulation of stimulating thyroid hormone and increased thyroid hormone (triiodothyronine and thyroxine) concentration in the blood. However, there is a decrease in thyroxine concentration in preterm infants (born before 37 weeks of gestation) due to the discontinuation of maternal thyroid hormone.

What Is Neonatal Hypothyroidism?

Neonatal hypothyroidism is a condition in the newborn child that occurs when normal thyroid hormone secretion is impaired. It is also known as congenital hypothyroidism. It is present from birth or can be acquired. The child suffering from neonatal hypothyroidism are born with inactive thyroid glands. In some rare cases, the thyroid gland has been absent since birth. As there is an anatomic defect in the thyroid gland, functional activities that are dependent on thyroid hormones are impaired. Neonatal hypothyroidism is more commonly seen in females.

What Are the Causes of Neonatal Hypothyroidism?

Listed below are the various cause of neonatal hypothyroidism:

• Anatomic Location of the Thyroid Gland - The abnormal thyroid gland location is also known as the ectopic thyroid gland.

• Thyroid Hypoplasia - Presence of underdeveloped thyroid gland.

• Thyroid Agenesis - Absent thyroid gland.

• Thyroid Dyshormonogenesis - The thyroid gland is present in a normal location but unable to make normal levels of thyroid hormones.

• Hashimoto Thyroiditis - In this condition, thyroid blocking antibody is passed from the mother to the child. Neonatal hypothyroidism in such cases is temporary. It lasts for a few weeks after the birth of the child.

• Medications - Antithyroid drugs and Sulfonamide drugs, if taken during pregnancy, can result in neonatal hypothyroidism as it disrupts thyroid hormone functions.

• Genetic Causes - Impaired thyroid hormone production due to genetic defect.

• Diet - Neonatal hypothyroidism is seen in a child if the mother does not take sufficient iodine during pregnancy.

• Iodine Intake - If the mother, during pregnancy, ingests a high amount of iodine in diet or supplements, the child develops neonatal hypothyroidism.

• Radioactive Iodine - If the mother is undergoing thyroid treatment for thyroid cancer during pregnancy, the child is at risk of neonatal hypothyroidism.

• Pituitary Hormone Deficiency - In this condition, the brain cannot obtain signals for releasing thyroid-stimulating hormones.

What Are the Clinical Features of Neonatal Hypothyroidism?

The signs and symptoms of neonatal hypothyroidism are present since birth or may develop slowly after a few months of life. Listed below are the clinical manifestation of neonatal hypothyroidism.

• The face of the child appears to be puffy.

• The tongue of the child is thick.

• There are large soft spots on the skull of the child.

• The child cries with a hoarse voice.

• The stomach of the child is distended with outpouching of the belly button.

• Difficulty in feeding and swallowing.

• The presence of flabby muscles with poor tone is also known as hypotonia.

• Yellowish discoloration of the eyes and skin.

• Difficulty in weight gain.

• Stunted growth.

• Lethargy.

• Abnormal bone growth and thickened facial features.

• Sleeping excessively.

• The skin of the child is pale, cold, and dry.

• The presence of swelling near the navel of the child is known as an umbilical hernia.

• Mental retardation and intellectual disability in children.

How Neonatal Is Hypothyroidism Diagnosed?

Newborns are screened for investigating the presence of signs and symptoms of hypothyroidism. A blood sample is taken from the child's heel and sent for laboratory investigation. The screening laboratory tests measure the concentration of the thyroxine and thyroxine stimulating hormones. If the stimulating thyroid hormone is increased and the thyroxine level is decreased, it is suggestive of neonatal hypothyroidism. The high level of thyroid-stimulated hormone is caused by the pituitary gland stimulating the thyroid gland. It eventually increases thyroid hormone. Blood samples from veins are also taken for the confirmation of the diagnosis. A thyroid function test is advised. Imaging procedures such as thyroid scans and ultrasonography can help identify the underlying cause.

What Are the Complications of Neonatal Hypothyroidism?

Listed below are the complication of neonatal hypothyroidism.

• Abnormal gait.

• Muscle spasm.

• Intellectual disability and inability to speak.

• Hearing and vision defects.

• Autistic behavior.

• Attention and memory disturbance.

What Are the Treatment for Neonatal Hypothyroidism?

A synthetic thyroid hormone known as levothyroxine is given to the child. It is available in tablet form. It is crushed and mixed with a small amount of liquid like water, breastmilk, and formula milk and given to the child. It is given to the child with a teaspoon or syringe. Parents should avoid mixing Levothyroxine with soya milk concentration as it binds with thyroxine and reduces its absorption.

How to Prevent Neonatal Hypothyroidism?

Certain measures can be followed to prevent neonatal hypothyroidism. According to the Institute of Medicine, a dietary allowance of 150 micrograms of iodine should be taken in a balanced diet by normal individuals, whereas 220 micrograms of iodine should be consumed during pregnancy. In addition, according to the American Thyroid Association, prenatal vitamins containing 150 micrograms of iodine should be given to pregnant and breastfeeding women.

Conclusion

Neonatal hypothyroidism refers to a severe deficiency of thyroid hormone in newborns. It results in impaired neurological function in children resulting in delayed growth and development. In addition, it affects the child's activity and brain development. Parents should be careful and observe signs and symptoms because if neonatal hypothyroidism is left untreated, it can cause potential complications such as developmental and neurologic disorders. Parents should seek immediate medical attention for their baby. Early diagnosis and adequate management can prevent irreversible nervous system damage in children.