Congenital hypothyroidism: causes, manifestations, treatment and possible consequences

Congenital hypothyroidism: causes, manifestations, treatment and possible consequences


Congenital hypothyroidism is a clinical syndrome that manifests itself during the neonatal period and is associated with a deficiency of thyroid hormones or insensitivity to them of body tissues. According to statistics, it is considered one of the most common among all congenital diseases of the endocrine glands. The average frequency of its occurrence is 1: 3500-4000. Moreover, in girls, this pathology is detected more often than in boys.

Causes

In most cases, congenital hypothyroidism is primary and is caused by damage to the rudiment of the thyroid gland during intrauterine development (at 4-9 weeks) due to radiation, treatment of the expectant mother with radioactive iodine or thyreostatic drugs. However, cases of secondary and even tertiary congenital hypothyroidism associated with pathology of the hypothalamic-pituitary system are possible.

The main causes of congenital hypothyroidism are:

  • malformations of the thyroid gland (complete absence of an organ or its underdevelopment, a combination of the latter with a dystopic location, when the glandular tissue is detected at the root of the tongue, trachea);
  • hereditary dys- or agenesis of the gland;
  • genetic defects in synthesis (violation of the capture and metabolism of iodine), secretion and metabolism of thyroid hormones;
  • insensitivity of tissue receptors to thyroid hormones;
  • hereditary resistance to thyroid-stimulating hormone;
  • iodine deficiency in a woman’s body during pregnancy;
  • malformations of the nervous system in the fetus;
  • damage to the pituitary gland as a result of trauma during childbirth;
  • pituitary aplasia;
  • congenital insufficiency of thyroid-stimulating hormone or thyroliberin, etc.


In some cases, hypothyroidism in a newborn can be transient if the pregnant woman has autoimmune thyroid diseases and the transmission of thyroid-blocking antibodies through the placenta. Sometimes a transient dysfunction of the gland is observed in premature or low birth weight infants as a result of intrauterine growth retardation.

Fundamentals of pathogenesis


All pathological changes in the body that occur during hypothyroidism are due to a lack of thyroid hormones. Since the latter perform many important functions and are involved in all types of metabolism, this significantly affects the development of the child.

First of all, the work of the nervous system is disrupted:

  • the total number of neurons decreases;
  • the amount of biologically active substances (neurotransmitters, peptides) in the nervous tissue decreases, which leads to a pronounced depression of the central nervous system;
  • differentiation of cells of the brain tissue suffers;
  • the process of myelination of nerve fibers slows down.


It should be noted that after reaching 4-6 weeks of age, these changes become almost irreversible.

With hypothyroidism, a decrease in protein synthesis and a violation of energy processes are observed, as a result of which:

  • the growth and differentiation of the bones of the skeleton slows down;
  • muscle performance decreases;
  • hematopoiesis is inhibited;
  • immunity is weakened;
  • enzymatic activity decreases (in the gastrointestinal tract, liver, kidneys).


In addition, in the body of patients, lipolysis slows down and the exchange of mucopolysaccharides is disrupted. A special substance, mucin, accumulates in the tissues, as a result of which they become edematous. That is why such children, despite their poor appetite, never look emaciated.

Clinical manifestations

The clinical picture of congenital hypothyroidism is characterized by a variety of symptoms. However, their severity varies from a latent course to manifest forms with pronounced symptoms. It is not so easy to identify this pathology immediately after birth, because its manifestations increase by 3-6 months. But this question is of fundamental importance, since the prognosis depends on the timeliness of the diagnosis and initiation of treatment. It is possible to suspect the presence of hypothyroidism in a newborn by a combination of signs:

  • high birth weight;
  • late discharge of meconium;
  • prolonged jaundice (up to 10 days);
  • dry skin;
  • low physical activity;
  • muscle hypotension;
  • sluggish sucking and poor appetite;
  • breathing disorders (noisy breathing, difficulty breathing through the nose, periods of apnea );
  • gastrointestinal problems (bloating and enlargement of the abdomen, constipation );
  • bradycardia ;
  • decrease in body temperature;
  • early anemia (difficult to treat).


Each of these symptoms individually is not pathognomonic, but their combination should alert the doctor and parents.

As the child develops, the clinical picture of hypothyroidism becomes more pronounced. The child lags behind peers in both physical and neuropsychic development. Him:

  • lethargy, weakness increase;
  • growth slows down;
  • the proportions of the body are violated (relative shortening of the limbs and fingers, thick neck, narrow eye slits, wide nose bridge);
  • teeth come out late;
  • edema appears (on the trunk, face, feet);
  • eyelids, lips, nostrils, tongue thicken (does not fit in the mouth);
  • the voice becomes low;
  • the fontanel does not close for a long time;
  • there is a pathology of the cardiovascular system (the boundaries of cardiac dullness expand, heart sounds become deaf, blood pressure decreases, systolic murmur can be heard);
  • an umbilical hernia is often detected .


In this case, the thyroid gland may not be detected (with underdevelopment) or increase in size (with pathology of hormone synthesis).

The manifestation of mild variants of congenital hypothyroidism can occur by 2-5 years of age and even during puberty. Usually, this can reveal growth retardation, sexual development, a decrease in intelligence and symptoms of myocardial dystrophy .

Diagnostics


Early diagnosis of hypothyroidism is very important. In order not to miss this pathology in a newborn, it is customary to use screening methods. To do this, on the 3-4th day of life, capillary blood is taken from the child to study the level of thyroid hormones and thyroid-stimulating hormone (TSH) of the pituitary gland. When positive (or questionable) results of the analysis are obtained, it is repeated, but at the same time, venous blood is taken for the study.

In areas without screening, newborns with at least two of the symptoms listed above should be screened.

In general, the diagnosis is based on a detailed analysis of clinical data and the results of additional research methods. The list of required examinations includes:

  • determination of the level of thyroid hormones and TSH;
  • general blood test (detects anemia, lipid metabolism disorders);
  • ultrasound examination of the gland;
  • electrocardiography ;
  • X-ray of the wrist joints (reveals the lagging behind the age norm of the rate of ossification processes).


It should be noted that changes on the radiograph and obvious metabolic disorders appear after 3-4 months of age.

Differential diagnosis for congenital hypothyroidism is carried out with the following pathological conditions:

  • Down syndrome ;
  • rickets ;
  • birth injury;
  • jaundice and anemia of various origins;
  • chondrodysplasia;
  • mucopolysaccharidosis , etc.


Treatment

The treatment of congenital hypothyroidism is based on lifelong replacement therapy. It starts from the moment the diagnosis is made, regardless of the possibility of laboratory confirmation. For this, L-thyroxine is used at a starting dose of 10-15 mcg per day. Gradually, the dose of the drug is increased, assessing the dynamics of clinical symptoms and the levels of hormones in the blood plasma.

The purpose of this treatment is to normalize the content of thyroid hormones in the blood and prevent damage to the central nervous system. The effectiveness of such treatment is evidenced by the active behavior of the child and the physiological dynamics of growth.

Additionally, such children can be assigned:

  • vitamins;
  • neurotrophic drugs (Cerebrolysin, Piracetam);
  • massage;
  • exercise therapy.


Forecast and possible consequences


With early diagnosis and timely treatment started (in the first month of life), the prognosis for the life and health of the child is favorable. Adequate replacement therapy can achieve good results. The child retains normal intelligence, and he does not lag behind in physical development from his peers.

With a late diagnosis, the prognosis is more serious, since changes in organs and tissues (especially in the nervous one) have already occurred. As a rule, in such cases, substitution therapy makes it possible to achieve physiological growth rates, but it is not able to completely eliminate the lag in the formation of intelligence. Without treatment, the disease is difficult and leads to irreversible impairment of the intellect and disability of the patient.

Which doctor to contact


If you suspect hypothyroidism in a child, you must contact a pediatrician, who, after the initial examination, will give a referral to an endocrinologist. Additionally, consultations of a neurologist and a cardiologist will be required.

Congenital hypothyroidism is one of the diseases with a serious prognosis, in which early diagnosis and adequate treatment help to avoid negative consequences, allow the child to develop normally and lead a normal life.

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