Diagnosis of congenital hypothyroidism

Identification of genetic pathologies in newborns is carried out in the first week after the baby is born. To make a diagnosis, the condition of the newborn is assessed using the Apgar scale. This system was developed by an American anesthesiologist, where each letter APGAR defines the following indicators:

• A (appearance) – color of the skin.
• P (puls) – pulse, heart rate.
• G (grimace) – grimaces, reflex excitability.
• A (activity) – activity of movements, muscle tone.
• R (respiration) – breathing pattern.

Each indicator is assessed by numbers from 0 to 2, that is, the overall result can be from 0 to 10. When congenital hypothyroidism is suspected, the most common signs of the disease are considered, and their significance is determined by the following points:

• Pregnancy more than 40 weeks or prematurity – 1 point.
• Birth weight over 4 kg – 1 point.
• Paleness of the skin – 1 point.
• Physiological jaundice for more than 3 weeks – 1 point.
• Swelling of the extremities and face – 2 points.
• Muscle weakness – 1 point.
• Big tongue – 1 point.
• Open posterior fontanelle – 1 point.
• Stool disorders (flatulence, constipation) – 2 points.
• Umbilical hernia – 2 points.

If the sum of points is more than 5, then this is a reason for further diagnostics of congenital anomalies, including those of the thyroid gland. Anamnestic data collection, an objective examination of the infant by a pediatrician, as well as a set of laboratory and instrumental studies are mandatory.

1. Objective data and anamnesis collection.

The disease can be suspected by its clinical symptoms. It is the first signs of hypothyroidism, due to its rare occurrence, that allow for early diagnosis. When collecting anamnesis, predisposing factors are established: heredity, diseases suffered by the woman during gestation and the general course of pregnancy.

2. Laboratory research.

A newborn's blood test (heel prick) is performed to check the level of TSH and thyroid hormones (neonatal screening). During pregnancy, an amniotic fluid test is used by puncturing the amniotic sac with a long needle. In hypothyroidism, a reduced level of T4 and increased TSH values are observed. A blood test for antibodies to the TSH receptor is also possible. If the TSH concentration is greater than 50 mIU/L, this indicates a problem.

3. Instrumental methods.

Thyroid ultrasound to determine the location of the organ and its development characteristics. When scanning newborns, the isotope 1-123 is used, which has a low radiation load. At the age of 3-4 months, the child undergoes X-rays of the legs to determine the true age of the skeletal system and identify a deficiency of thyroid hormones.

There are also special tests to determine indicators of mental development (IQ). They are used to assess the condition of children over one year old and when the visual symptoms of hypothyroidism are blurred.

Screening for congenital hypothyroidism

For early diagnosis of more than 50 genetic pathologies, all newborns undergo screening. Blood tests are performed during the first 10 days of life. Screening for congenital thyroid diseases is performed for the following reasons:

• High incidence of congenital hypothyroidism.
• High sensitivity of the method.
• Most clinical signs of the disease appear after three months of the child's life.
• Early diagnosis and treatment can prevent mental retardation and other irreversible complications.

To detect the anomaly, a neonatal test for thyrotropin (TSH) and thyroxine (T4) is used. Blood is taken using a percutaneous puncture from the heel on the 4th-5th day after birth in full-term babies and on the 7th-14th day in premature babies.

Most often, screening is performed for TSH, possible test results:

• TSH less than 20 mIU/L is normal.
• TSH 20-50 mIU/L – repeat examination is necessary.
• TSH above 50 mIU/L – suspected hypothyroidism.
• TSH above 50 mIU/L – emergency treatment with thyroxine is required.
• TSH more than 100 mIU/L – congenital hypothyroidism.

In order for the test results to be reliable, blood is given on an empty stomach, 3-4 hours after the last feeding. The analysis is carried out 4-5 days after the start of lactation. Laboratory screening in 3-9% of cases gives false negative results. Therefore, when making a diagnosis, clinical symptoms and the results of other studies are taken into account.

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Tests

Laboratory tests are a mandatory component of diagnostics of various congenital anomalies, including hypothyroidism. The following set of tests is indicated to detect the disease:

• General blood test for normochromic anemia.
• Biochemical blood test for excess lipoproteins and hypercholesterolemia.
• Level of free and total T3, T4.
• Determination of TSH and antibodies to its receptors.
• Antimicrosomal antibodies AMS.
• Calcitonin and other thyroid hormones.

Let's look at the main tests prescribed when endocrine pathologies are suspected and their interpretation:

1. TSH is a hormone produced by the pituitary gland for normal thyroid function, stabilization of physiological processes in the central nervous system and metabolic processes in the body. If its values exceed the norm, this indicates disturbances in the body. The optimal value of TSH is considered to be 0.4-4.0 mIU/l, results above or below this norm are a symptom of hypothyroidism.
2. T3 and T4 are amino acid thyroid hormones, thyroxine (T4) and triiodothyronine (T3). They are produced by the follicular cells of the organ under the control of TSH. They provide biological and metabolic activity of the body. They affect the functional abilities of the central nervous system, memory, psyche, and immune system.
3. Antibody analysis – the immune system works in such a way that when a disease occurs, antibodies are produced. If the disease is autoimmune, autoantibodies are synthesized that attack the patient’s healthy tissues. In this case, the thyroid gland is one of the first to be targeted.

In order for the laboratory test results to be reliable, it is necessary to properly prepare for the tests. Blood is taken only on an empty stomach. In newborns, blood is taken from the heel.

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Instrumental diagnostics

If hypothyroidism is suspected, the patient is prescribed a set of various diagnostic methods, including instrumental ones. They are necessary to establish the cause that caused the disease, to clarify the features of the course of the pathological process and the general condition of the body.

Instrumental diagnostics of thyroid insufficiency consists of:

• Ultrasound of the thyroid gland (study of structure, homogeneity, density).
• Ultrasound of the adrenal glands.
• CT and MRI of the head.
• ECG and Doppler ultrasonography of blood vessels.
• Thyroid scintigraphy (a test of organ functionality using radioactive isotopes introduced into the body).
• Histology and cytology of thyroid biopsy material.
• Examination by related specialists: gynecologist/urologist, neurologist, cardiologist.

If the pathology occurs with goiter, then instrumental methods reveal changes in the echostructure of organ tissues: decreased echogenicity, focal changes, heterogeneous structure. Other forms of the disease have similar symptoms. In order to verify the diagnosis, in most cases a puncture biopsy is performed using a thin needle, as well as a dynamic study of TSH and comparison of the results with the symptoms of the anomaly.

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Differential diagnostics

A set of tests for congenital hypothyroidism does not always allow for reliable confirmation of the pathology. Differential diagnostics is necessary to compare endocrine system anomalies with other diseases with similar symptoms.

First of all, thyroid insufficiency is differentiated from the following disorders:

• Down syndrome.
• Rickets.
• Jaundice of unknown etiology.
• Birth injuries.
• Different types of anemia.

In older children, the disease is associated with:

• Physical and mental retardation.
• Pituitary dwarfism.
• Chondrodysplasia.
• Congenital dysplasia.
• Heart defects.

During diagnostics, it is taken into account that some diseases, such as: cardiac, renal and hepatic failure, myocardial infarction, lead to a violation of the enzyme 5-deiodinase. This entails a decrease in the level of triiodothyronine with normal T3 and T4.

Very often hypothyroidism is mistaken for chronic glomerulonephritis, since both diseases have a similar symptom complex. A comparison with circulatory failure is also made. For differentiation, the patient is prescribed a general blood and urine test, BAC studies, T3 and T4 levels, thyroid ultrasound and its radioisotope scanning.

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